Validation of the diagnosis of venous thromboembolism in general practice database studies

Tea Consumption, Milk or Sweeteners Addition, Genetic Variation in Caffeine Metabolism, and Incident Venous Thromboembolism

OBJECTIVE

 The association between tea consumption and venous thromboembolism (VTE) remains unknown. We aimed to evaluate the association between tea consumption with different additives (milk and/or sweeteners) and incident VTE, and the modifying effects of genetic variation in caffeine metabolism on the association.

METHODS

 A total of 190,189 participants with complete dietary information and free of VTE at baseline in the UK Biobank were included. The primary outcome was incident VTE, including incident deep vein thrombosis and pulmonary embolism.

RESULTS

 During a median follow-up of 12.1 years, 4,485 (2.4%) participants developed incident VTE. Compared with non-tea drinkers, tea drinkers who added neither milk nor sweeteners (hazard ratio [HR]: 0.85; 95% confidence interval [95% CI]: 0.76-0.94), only milk (HR: 0.86; 95% CI: 0.80-0.93), and both milk and sweeteners to their tea (HR: 0.90; 95% CI: 0.81-0.99) had a lower risk of VTE, while those who added only sweeteners to their tea did not (HR: 0.94; 95% CI: 0.75-1.17). Moreover, there was an L-shaped relationship between tea consumption and incident VTE among tea drinkers who added neither milk nor sweeteners, only milk, and both milk and sweeteners to their tea, respectively. However, a nonsignificant association was found among tea drinkers who added only sweeteners to their tea. Genetic variation in caffeine metabolism did not significantly modify the association (p-interaction = 0.659).

CONCLUSION

 Drinking unsweetened tea, with or without added milk, was associated with a lower risk of VTE. However, there was no significant association between drinking tea with sweeteners and incident VTE.

Evaluation of venous thromboembolism risk assessment models for hospital inpatients: the VTEAM evidence synthesis

Background

Pharmacological prophylaxis during hospital admission can reduce the risk of acquired blood clots (venous thromboembolism) but may cause complications, such as bleeding. Using a risk assessment model to predict the risk of blood clots could facilitate selection of patients for prophylaxis and optimise the balance of benefits, risks and costs.

Objectives

We aimed to identify validated risk assessment models and estimate their prognostic accuracy, evaluate the cost-effectiveness of different strategies for selecting hospitalised patients for prophylaxis, assess the feasibility of using efficient research methods and estimate key parameters for future research.

Design

We undertook a systematic review, decision-analytic modelling and observational cohort study conducted in accordance with Enhancing the QUAlity and Transparency Of health Research (EQUATOR) guidelines.

Setting

NHS hospitals, with primary data collection at four sites.

Participants

Medical and surgical hospital inpatients, excluding paediatric, critical care and pregnancy-related admissions.

Interventions

Prophylaxis for all patients, none and according to selected risk assessment models.

Main outcome measures

Model accuracy for predicting blood clots, lifetime costs and quality-adjusted life-years associated with alternative strategies, accuracy of efficient methods for identifying key outcomes and proportion of inpatients recommended prophylaxis using different models.

Results

We identified 24 validated risk assessment models, but low-quality heterogeneous data suggested weak accuracy for prediction of blood clots and generally high risk of bias in all studies. Decision-analytic modelling showed that pharmacological prophylaxis for all eligible is generally more cost-effective than model-based strategies for both medical and surgical inpatients, when valuing a quality-adjusted life-year at £20,000. The findings were more sensitive to uncertainties in the surgical population; strategies using risk assessment models were more cost-effective if the model was assumed to have a very high sensitivity, or the long-term risks of post-thrombotic complications were lower. Efficient methods using routine data did not accurately identify blood clots or bleeding events and several pre-specified feasibility criteria were not met. Theoretical prophylaxis rates across an inpatient cohort based on existing risk assessment models ranged from 13% to 91%.

Limitations

Existing studies may underestimate the accuracy of risk assessment models, leading to underestimation of their cost-effectiveness. The cost-effectiveness findings do not apply to patients with an increased risk of bleeding. Mechanical thromboprophylaxis options were excluded from the modelling. Primary data collection was predominately retrospective, risking case ascertainment bias.

Conclusions

Thromboprophylaxis for all patients appears to be generally more cost-effective than using a risk assessment model, in hospitalised patients at low risk of bleeding. To be cost-effective, any risk assessment model would need to be highly sensitive. Current evidence on risk assessment models is at high risk of bias and our findings should be interpreted in this context. We were unable to demonstrate the feasibility of using efficient methods to accurately detect relevant outcomes for future research.

Future work

Further research should evaluate routine prophylaxis strategies for all eligible hospitalised patients. Models that could accurately identify individuals at very low risk of blood clots (who could discontinue prophylaxis) warrant further evaluation.

Study registration

This study is registered as PROSPERO CRD42020165778 and Researchregistry5216.

Funding

This award was funded by the National Institute for Health and Care Research (NIHR) Health Technology Assessment programme (NIHR award ref: NIHR127454) and will be published in full in Health Technology Assessment; Vol. 28, No. 20. See the NIHR Funding and Awards website for further award information.

The risk of venous thromboembolism in atopic dermatitis: a matched cohort analysis in UK primary care

BACKGROUND

Atopic dermatitis (AD) is a common chronic inflammatory skin condition. While other chronic inflammatory conditions are associated with increased risk of venous thromboembolism (VTE), associations between AD and VTE have not been established.

OBJECTIVES

We examined whether AD is associated with an increased risk of VTE in a population-based study.

METHODS

Electronic health records were extracted from UK general practices contributing to the Optimum Patient Care Research Database (1 January 2010 to 1 January 2020). All adults with AD were identified (n = 150 975) and age- and sex-matched with unaffected controls (n = 603 770). The risk of VTE, consisting of pulmonary embolism (PE) or deep-vein thrombosis (DVT), was compared in people with AD vs. controls using Cox proportional hazard models. PE and DVT were examined separately as secondary outcomes.

RESULTS

We identified 150 975 adults with active AD and matched them with 603 770 unaffected controls. During the study, 2576 of those with active AD and 7563 of the matched controls developed VTE. Individuals with AD had a higher risk of VTE than controls [adjusted hazard ratio (aHR) 1.17, 95% confidence interval (CI) 1.12-1.22]. When assessing VTE components, AD was associated with a higher risk of DVT (aHR 1.30, 95% CI 1.23-1.37) but not PE (aHR 0.94, 95% CI 0.87-1.02). The VTE risk was greater in older people with AD (≥ 65 years: aHR 1.22, 95% CI 1.15-1.29; 45-65 years: aHR 1.15, 95% CI 1.05-1.26; < 45 years: aHR 1.07, 95% CI 0.97-1.19) and those with obesity [body mass index (BMI) ≥ 30: aHR 1.25, 95% CI 1.12-1.39; BMI < 30: aHR 1.08, 95% CI 1.01-1.15). Risk was broadly consistent across mild, moderate or severe AD.

CONCLUSIONS

AD is associated with a small increase in risk of VTE and DVT, with no increase in risk of PE. The magnitude of this risk increase is modest in younger people, and those without obesity.

Venous thromboembolism following colectomy for diverticular disease: an English population-based cohort study

AIM

This study reports venous thromboembolism (VTE) rates following colectomy for diverticular disease to explore the magnitude of postoperative VTE risk in this population and identify high risk subgroups of interest.

METHOD

English national cohort study of colectomy patients between 2000 and 2019 using linked primary (Clinical Practice Research Datalink) and secondary (Hospital Episode Statistics) care data. Stratified by admission type, absolute incidence rates (IR) per 1000 person-years and adjusted incidence rate ratios (aIRR) were calculated for 30- and 90-day post-colectomy VTE.

RESULTS

Of 24,394 patients who underwent colectomy for diverticular disease, over half (57.39%) were emergency procedures with the highest VTE rate seen in patients ≥70-years-old (IR 142.27 per 1000 person-years, 95%CI 118.32-171.08) at 30 days post colectomy. Emergency resections (IR 135.18 per 1000 person-years, 95%CI 115.72-157.91) had double the risk (aIRR 2.07, 95%CI 1.47-2.90) of developing a VTE at 30 days following colectomy compared to elective resections (IR 51.14 per 1000 person-years, 95%CI 38.30-68.27). Minimally invasive surgery (MIS) was shown to be associated with a 64% reduction in VTE risk (aIRR 0.36 95%CI 0.20-0.65) compared to open colectomies at 30 days post-op. At 90 days following emergency resections, VTE risks remained raised compared to elective colectomies.

CONCLUSION

Following emergency colectomy for diverticular disease, the VTE risk is approximately double compared to elective resections at 30 days while MIS was found to be associated with a reduced risk of VTE. This suggests advancements in postoperative VTE prevention in diverticular disease patients should focus on those undergoing emergency colectomies.

Blood pressure and risk of venous thromboembolism: a cohort analysis of 5.5 million UK adults and Mendelian randomization studies

AIMS

Evidence for the effect of elevated blood pressure (BP) on the risk of venous thromboembolism (VTE) has been conflicting. We sought to assess the association between systolic BP and the risk of VTE.

METHODS AND RESULTS

Three complementary studies comprising an observational cohort analysis, a one-sample and two-sample Mendelian randomization were conducted using data from 5 588 280 patients registered in the Clinical Practice Research Datalink (CPRD) dataset and 432 173 UK Biobank participants with valid genetic data. Summary statistics of International Network on Venous Thrombosis genome-wide association meta-analysis was used for two-sample Mendelian randomization. The primary outcome was the first occurrence of VTE event, identified from hospital discharge reports, death registers, and/or primary care records. In the CPRD cohort, 104 017(1.9%) patients had a first diagnosis of VTE during the 9.6-year follow-up. Each 20 mmHg increase in systolic BP was associated with a 7% lower risk of VTE [hazard ratio: 0.93, 95% confidence interval (CI): (0.92-0.94)]. Statistically significant interactions were found for sex and body mass index, but not for age and subtype of VTE (pulmonary embolism and deep venous thrombosis). Mendelian randomization studies provided strong evidence for the association between systolic BP and VTE, both in the one-sample [odds ratio (OR): 0.69, (95% CI: 0.57-0.83)] and two-sample analyses [OR: 0.80, 95% CI: (0.70-0.92)].

CONCLUSION

We found an increased risk of VTE with lower BP, and this association was independently confirmed in two Mendelian randomization analyses. The benefits of BP reduction are likely to outweigh the harms in most patient groups, but in people with predisposing factors for VTE, further BP reduction should be made cautiously.

Accuracy of efficient data methods to determine the incidence of hospital-acquired thrombosis and major bleeding in medical and surgical inpatients: a multicentre observational cohort study in four UK hospitals

OBJECTIVES

We evaluated the accuracy of using routine health service data to identify hospital-acquired thrombosis (HAT) and major bleeding events (MBE) compared with a reference standard of case note review.

DESIGN

A multicentre observational cohort study.

SETTING

Four acute hospitals in the UK.

PARTICIPANTS

A consecutive unselective cohort of general medical and surgical patients requiring hospitalisation for a period of >24 hours during the calendar year 2021. We excluded paediatric, obstetric and critical care patients due to differential risk profiles.

INTERVENTIONS

We compared preidentified sources of routinely collected information (using hospital coding data and local contractually mandated thrombosis datasets) to data extracted from case notes using a predesigned workflow methodology.

PRIMARY AND SECONDARY OUTCOME MEASURES

We defined HAT as objectively confirmed venous thromboembolism occurring during hospital stay or within 90 days of discharge and MBE as per international consensus.

RESULTS

We were able to source all necessary routinely collected outcome data for 87% of 2008 case episodes reviewed. The sensitivity of hospital coding data (International Classification of Diseases 10th Revision, ICD-10) for the diagnosis of HAT and MBE was 62% (95% CI, 54 to 69) and 38% (95% CI, 27 to 50), respectively. Sensitivity improved to 81% (95% CI, 75 to 87) when using local thrombosis data sets.

CONCLUSIONS

Using routinely collected data appeared to miss a substantial proportion of outcome events, when compared with case note review. Our study suggests that currently available routine data collection methods in the UK are inadequate to support efficient study designs in venous thromboembolism research.

TRIAL REGISTRATION NUMBER

NIHR127454.

Time trends in the incidence rates of venous thromboembolism following colorectal resection by indication and operative technique

AIM

It is important for patient safety to assess if international changes in perioperative care, such as the focus on venous thromboembolism (VTE) prevention and minimally invasive surgery, have reduced the high post colectomy VTE risks previously reported. This study assesses the impact of changes in perioperative care on VTE risk following colorectal resection.

METHOD

This was a population-based cohort study of colectomy patients in England between 2000 and 2019 using a national database of linked primary (Clinical Practice Research Datalink) and secondary (Hospital Episode Statistics) care data. Within 30 days following colectomy, absolute VTE rates per 1000 person-years and adjusted incidence rate ratios (aIRRs) using Poisson regression for the per year change in VTE risk were calculated.

RESULTS

Of 183 791 patients, 1337 (0.73%) developed 30-day postoperative VTE. Overall, VTE rates reduced over the 20-year study period following elective (relative risk reduction 31.25%, 95% CI 5.69%-49.88%) but not emergency surgery. Similarly, yearly changes in VTE risk reduced following minimally invasive resections (elective benign, aIRR 0.93, 95% CI 0.90-0.97; elective malignant, aIRR 0.94, 95% CI 0.91-0.98; and emergency benign, aIRR 0.96, 95% CI 0.92-1.00) but not following open resections. There was a per year VTE risk increase following open emergency malignant resections (aIRR 1.02, 95% CI 1.00-1.04).

CONCLUSION

Yearly VTE risks reduced following minimally invasive surgeries in the elective setting yet in contrast were static following open elective colectomies, and following emergency malignant resections increased by almost 2% per year. To reduce VTE risk, further efforts are required to implement advances in surgical care for those having emergency and/or open surgery.

The Duration and Magnitude of Postdischarge Venous Thromboembolism Following Colectomy

OBJECTIVE

To assess the impact of current guidelines by reporting weekly postoperative postdischarge venous thromboembolism (VTE) rates.

SUMMARY BACKGROUND DATA

Disparity exists between the postoperative thromboprophylaxis duration colectomy patients receive based on surgical indication, where malignant resections routinely receive 28 days extended thromboprophylaxis into the postdischarge period and benign resections do not.

METHODS

English national cohort study of colectomy patients between 2010 and 2019 using linked primary (Clinical Practice Research Datalink) and secondary (Hospital Episode Statistics) care data. Stratified by admission type and surgical indication, absolute incidence rates (IRs) per 1000 person-years and adjusted incidence rate ratios (aIRRs) for postdischarge VTE were calculated for the first 4 weeks following resection and postdischarge VTE IRs for each postoperative week to 12 weeks postoperative.

RESULTS

Of 104,744 patients, 663 (0.63%) developed postdischarge VTE within 12 weeks after colectomy. Postdischarge VTE IRs per 1000 person-years for the first 4 weeks postoperative were low following elective resections [benign: 20.66, 95% confidence interval (CI): 13.73-31.08; malignant: 28.95, 95% CI: 23.09-36.31] and higher following emergency resections (benign: 47.31, 95% CI: 34.43-65.02; malignant: 107.18, 95% CI: 78.62-146.12). Compared with elective malignant resections, there was no difference in postdischarge VTE risk within 4 weeks following elective benign colectomy (aIRR=0.92, 95% CI: 0.56-1.50). However, postdischarge VTE risks within 4 weeks following emergency resections were significantly greater for benign (aIRR=1.89, 95% CI: 1.22-2.94) and malignant (aIRR=3.13, 95% CI: 2.06-4.76) indications compared with elective malignant colectomy.

CONCLUSIONS

Postdischarge VTE risk within 4 weeks of colectomy is ∼2-fold greater following emergency benign compared with elective malignant resections, suggesting emergency benign colectomy patients may benefit from extended VTE prophylaxis.

Menopausal Hormone Therapy Formulation and Breast Cancer Risk

OBJECTIVE

To evaluate whether the increased risk of breast cancer is dependent on the formulation of menopausal hormone therapy (HT) used.

METHODS

We performed a population-based case-control study of women aged 50 years or older using data from the U.K. Clinical Practice Research Datalink. Women with incident cases of breast cancer were age-matched (1:10) with a control group of women with comparable follow-up time with no history of breast cancer. Exposures were classified as ever or never for the following menopausal HT formulations: bioidentical estrogens, animal-derived estrogens, micronized progesterone, and synthetic progestin. Logistic regression analyses were performed to estimate the adjusted effect of menopausal HT formulation on breast cancer risk.

RESULTS

Between 1995 and 2014, 43,183 cases of breast cancer were identified and matched to 431,830 women in a control group. In adjusted analyses, compared with women who never used menopausal HT, its use was associated with an increased risk of breast cancer (odds ratio [OR] 1.12, 95% CI 1.09-1.15). Compared with never users, estrogens were not associated with breast cancer (bioidentical estrogens: OR 1.04, 95% CI 1.00-1.09; animal-derived estrogens: OR 1.01, 95% CI 0.96-1.06; both: OR 0.96, 95% CI 0.89-1.03). Progestogens appeared to be differentially associated with breast cancer (micronized progesterone: OR 0.99, 95% CI 0.55-1.79; synthetic progestin: OR 1.28, 95% CI 1.22-1.35; both OR 1.31, 0.30-5.73).

CONCLUSION

Although menopausal HT use appears to be associated with an overall increased risk of breast cancer, this risk appears predominantly mediated through formulations containing synthetic progestins. When prescribing menopausal HT, micronized progesterone may be the safer progestogen to be used.

Validation of Postsurgical Venous Thromboembolism Diagnoses of Patients Undergoing Lower Limb Orthopedic Surgery in the Danish National Patient Registry

Background

Healthcare databases can be a valuable source of epidemiological research regarding postoperative venous thromboembolism (VTE), ie, deep vein thrombosis (DVT) and pulmonary embolism (PE), following orthopedic procedures, but only if the diagnoses are valid. We examined the validity of VTE diagnosis codes in the Danish National Patient Registry (DNPR) by calculating their positive predictive value (PPV) and negative predictive value (NPV) versus actual medical records.

Methods

We identified patients who had undergone lower limb surgery during the period 2009–2019 at a hospital in the North Denmark Region. Of these, 420 patients had at least one VTE diagnosis registered in the DNPR within 180 days after lower limb surgery. Each patient with a VTE diagnosis was matched with two patients on age and sex, as well as type, location and period of surgery. The entire medical record and diagnostic imaging were reviewed to confirm VTE diagnosis.

Results

The overall PPVs was 85.2% (95% CI: 81.5–88.5%) for first time VTE diagnosis following lower limb surgery, 82.6% (95% CI: 77.5–82.8%) for DVT, and 90.3% (95% CI: 84.3–94.6%) for PE. We found improvement in PPV during the study period when stratifying for three periods of the whole period. There were no significant differences when stratifying for sex, age, or surgery site. All negative predictive values were higher than 99%. A total of 113 additional VTE diagnoses were registered among 88 VTE patients during follow-up. Only four of the suspected recurrent VTEs were confirmed to be true recurrent VTEs.

Conclusion

The VTE diagnosis codes in the DNPR after lower limb orthopedic surgery were highly valid against the actual medical records, and we observed better PPV over recent years.

Glucocorticoids and Risk of Venous Thromboembolism in Asthma Patients Aged 20-59 Years in the United Kingdom's CPRD 1995-2015

BACKGROUND

Glucocorticoids, the class of steroids used in management of asthma, have been observed to be associated with adverse events such as increased coagulation and inhibition of fibrinolysis. This study evaluated the risk of VTE in relation to the use of glucocorticoids in patients with asthma.

METHODS

We conducted a nested case-control study among patients aged 20-59 years with asthma who received at least one glucocorticoid prescription during 1995-2015 in the UK-based Clinical Practice Research Datalink GOLD. We used descriptive analyses and conditional logistic regression to evaluate the risk of VTE associated with glucocorticoid use.

RESULTS

The adjusted ORs (aORs) (95% CI) for VTE in patients exposed to glucocorticoids were 1.9 (1.6-2.3), 1.4 (1.1-1.8), and 1.2 (0.9-1.5) for current, recent, and past glucocorticoid users, respectively, compared to the unexposed. The aORs (95% CI) for VTE in patients exposed to systemic glucocorticoid and inhaled glucocorticoids, compared to the unexposed, were 3.5 (2.7-4.5) and 1.5 (1.3-1.8), respectively.

CONCLUSION

Current and systemic glucocorticoid use was associated with a dose-response increased risk of incident idiopathic VTE.

Risk of venous thromboembolism in immune-mediated inflammatory diseases: a UK matched cohort study

Objectives

To describe the risk of venous thromboembolism (VTE), and risk factors for VTE, in people with immune-mediated inflammatory diseases (IMID) (ulcerative colitis, Crohn’s disease (CD), rheumatoid arthritis (RA) and psoriatic arthritis (PsA)), compared with a matched control population.

Methods

A total of 53 378 people with an IMID were identified over 1999–2019 in the UK Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) primary care database and were matched to 213 512 people without an IMID. The association between the presence of any IMID, and each IMID separately, and risk of VTE was estimated using unadjusted and multivariable-adjusted Cox proportional hazards models. The prevalence of VTE risk factors, and associations between VTE risk factors and risk of VTE, were estimated in people with and without an IMID.

Results

People with an IMID were at increased risk of VTE (adjusted HR [aHR] 1.46, 95% CI 1.36,1.56), compared with matched controls. When assessing individual diseases, risk was increased for CD (aHR 1.74, 95% CI 1.45 to 2.08), ulcerative colitis (aHR 1.27, 95% CI 1.10 to 1.45) and RA (aHR 1.54, 95% CI 1.40 to 1.70) but there was no evidence of an association for PsA (aHR 1.21, 95% CI 0.96 to 1.52). In people with an IMID, independent risk factors for VTE included male sex, overweight/obese body mass index, current smoking, history of fracture, and, across study follow-up, abnormal platelet count.

Conclusions

VTE risk is increased in people with IMIDs. Routinely available clinical information may be helpful to identify individuals with an IMID at increased future risk of VTE.

Observational study registration number

Clinicaltrials.gov (NCT03835780).

The Risk of Venous Thromboembolism (VTE) in Men with Benign Prostatic Hyperplasia Treated with 5-Alpha Reductase Inhibitors (5ARIs)

Background

Many men receive 5-alpha reductase inhibitors (5ARIs) for ongoing treatment of benign prostatic hyperplasia (BPH). The increased risk of cardiovascular complications with 5ARIs has been documented in BPH studies and the occurrence of cerebral venous thrombosis, presumably due to increased estrogen level following 5ARI use, was described in multiple case reports. The objective of this study was to determine if 5ARIs with or without alpha blockers (AB) were associated with an increased risk of venous thromboembolism (VTE) in males with BPH.

Methods

We conducted a nested case–control study among a population of men ages 40–79 who received at least one 5ARI or AB prescription for treatment of BPH between 1995 and 2015 in the UK-based Clinical Practice Research Datalink GOLD. Cases of incident VTE (pulmonary embolism [PE] or deep venous thrombosis [DVT]) and matched controls were identified from this population. We used descriptive analyses and conditional logistic regression to evaluate the risk of VTE in users of 5ARIs compared to users of ABs.

Results

For 5ARI only users, the adjusted odds ratios (aORs), (95% CI) for VTE were 1.51 (0.98–2.32) in current 5ARI users and 1.23 (0.70–2.17) in recent/distant past, compared to AB only users. However, the aOR (95% CI) in men who had 50 or more current 5ARI prescriptions compared to users of ABs only was higher: 2.29 (1.14–4.63). For 5ARI with AB use, the aORs, (95% CI) for VTE were 1.16 (0.64–2.10) in current 5ARI+AB users and 1.93 (0.71–5.25) in recent/distant past, compared to AB only users. The aOR (95% CI) in men who had 50 or more current 5ARI+AB prescriptions compared to users of ABs only was 1.65 (0.64–4.26).

Conclusion

Current use of 5ARI, particularly long-term use, is associated with an increased risk of incident idiopathic VTE compared to patients treated with AB use only.

External validation of a model to predict women most at risk of postpartum venous thromboembolism: Maternity clot risk

INTRODUCTION

Venous thromboembolism (VTE) is the leading cause of direct maternal mortality in high-income countries. We previously developed a risk prediction score for postpartum venous thromboembolism (VTE) in women without a previous VTE. In this paper, we provide further external validation and assess its performance across various groups of postpartum women from England.

MATERIALS AND METHODS

Cohort study using primary and secondary care data covering England. We used data from QResearch comprising women with pregnancies ending in live birth or stillbirth recoded in Hospital Episodes Statistics between 2004 and 2015. Outcome was VTE in the 6 weeks postpartum. Our predictor variables included sociodemographic and lifestyle characteristics, pre-existing comorbidities, and pregnancy and delivery characteristics.

RESULTS

Among 535,583 women with 700,185 deliveries, 549 VTE events were recorded (absolute risk of 7.8 VTE events per 10,000 deliveries). When we compared predicted probabilities of VTE for each woman from the original model with actual VTE events, we obtained a C-statistic of 0.67 (95% CI 0.65 to 0.70). However, our model slightly over-predicted VTE risk for the higher risk women (calibration slope = 0.84; 95% CI 0.74 to 0.94). Performance was similar across groups defined by calendar time, socioeconomic status, age group and geographical area. The score performed comparably with the existing algorithm used by the UK Royal College of Obstetrician and Gynaecologists.

CONCLUSIONS

Our model enables flexibility in setting new treatment thresholds. Adopting it in clinical practice may help optimise use of low-molecular-weight heparin postpartum to maximise health gain by better targeting of high-risk groups.

Receipt of anticoagulation after venous thromboembolism diagnoses during delivery hospitalizations

INTRODUCTION

Obstetric venous thromboembolism (VTE) is a leading cause of maternal mortality. While hospital discharge data provide a readily accessible means of studying this relatively rare outcome, diagnosis codes are of limited validity. Prior studies have demonstrated that VTE billing codes may be subject to misclassification and false positives and overestimate obstetric VTE risk. Given the public health significance of accurately estimating obstetric VTE, the purpose of this study was to determine to what degree patients received anticoagulants after discharge from a delivery hospitalization associated with an acute VTE diagnosis as pharmacy claims may more accurately assess the incidence of obstetric VTE.

STUDY DESIGN

A retrospective cohort study using the MarketScan database was performed using 2008-2014 claims data. We identified women 15-54 years of age diagnosed with acute VTE during a delivery hospitalization. We determined the proportion of women with VTE that received anticoagulants within 60 days of delivery discharge. Only women with ≥60 days of pharmacy benefits after discharge were included. Receipt of low molecular weight and unfractionated heparin, warfarin, and Xa inhibitors was ascertained. Receipt of anticoagulants was analyzed individually based on diagnoses for deep vein thrombosis (DVT), pulmonary embolism (PE), or both. The Chi-square test was performed for categorical comparisons.

RESULTS

Of 2,664,951 delivery hospitalizations, 2112 women had a diagnosis of VTE (0.08%) including 236 women with PE alone, 1760 women with DVT alone, and 116 women with both DVT and PE. Of these women, 51.3% (95% CI 49.2-53.4%) received an anticoagulant including 49.5% of women with DVT (95% CI 47.2-51.8%), 50.0% of women with PE (95% CI 43.7-56.3%), and 81.9% of women with both DVT and PE (95% CI 73.9-87.9%).

CONCLUSION

This analysis of pharmacy claims found that estimates for the proportion of deliveries with acute VTE diagnoses that subsequently received anticoagulants was similar to chart-confirmed VTE, albeit in a large population. In addition to previous studies comparing database claims to chart review that showed that the prevalence of VTE was grossly overestimated, these findings support that the proportion of cases with VTE during delivery hospitalization may be approximately half that ascertained with billing codes.

Comparative cardiovascular safety of strontium ranelate and bisphosphonates: a multi-database study in 5 EU countries by the EU-ADR Alliance

Strontium ranelate use, compared with oral bisphosphonates, is not associated with increased risk of AMI in patients with no contraindications for SR use. However, current strontium ranelate (compared with current bisphosphonate) appears associated with 25-30% excess risk of VTE and 35% excess risk of CVDeath.

INTRODUCTION

Evaluate the risk of cardiac and thromboembolic events among new users of SR and oral BPs without contraindications for SR.

METHODS

We conducted three multi-national, multi-database (Aarhus-Denmark, HSD-Italy, IPCI-Netherlands, SIDIAP-Spain, THIN-UK) case-control studies nested within a cohort of new users of SR/BP. We matched cases of acute myocardial infarction (AMI), venous thromboembolism (VTE), and cardiovascular death (CVDeath), up to 10 controls on gender, year of birth, index date, and country. Conditional logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (CIs) according to current SR vs current BP use and current vs past SR use, adjusting for potential confounders. Data were pooled using random effects meta-analysis.

RESULTS

No excess risk of AMI (5477 cases/54,674 controls) was found with current SR vs current BP (OR 0.89 (95%CI 0.70, 1.12)) nor with current vs past SR use (0.71(0.56, 0.91)). For VTE (5614 cases/6036 controls), an excess risk was found with current SR compared with current BP use, 1.24 (0.96, 1.61), and current vs past SR use, 1.30 (1.04, 1.62). For CVDeath (3019 cases/29,871 controls), an increased risk was seen with current SR vs current BP use, 1.35 (1.02, 1.80), but not with current vs past SR use (0.68 (0.48, 0.96)).

CONCLUSION

In patients without contraindications for SR, we found no evidence of an increased risk of AMI but a 25-30% excess risk of VTE and a 35% excess risk of CVDeath with current SR vs current BP users. This is despite a reduction in risk in CVDeath with current vs past SR users. The latter disparity could still be partially explained by cessation of preventative therapies in end-of-life or residual confounding by indication.

Validation of venous thromboembolism diagnoses in patients receiving rivaroxaban or warfarin in The Health Improvement Network

Purpose

To describe the effect that validation of venous thromboembolism (VTE) coded entries in the health improvement network (THIN) has on incidence rates of VTE among a cohort of rivaroxaban/warfarin users.

Methods

Among 36 701 individuals with a first prescription for rivaroxaban/warfarin between 2012 and 2015, we performed a two‐step VTE case identification process followed by a two‐step case validation process involving manual review of patient records. A valid case required a coded entry for VTE at some point after their first rivaroxaban/warfarin prescription with evidence of referral/hospitalization either as a coded entry or entered as free text. Positive predictive values (PPVs) with 95% confidence intervals (CIs) were calculated using validated cases as the gold standard. Incidence rates were calculated per 1000 person‐years with 95% CIs.

Results

We identified 2166 patients with a coded entry of VTE after their initial rivaroxaban/warfarin prescription; incidence rate of 45.31 per 1000 person‐years (95% CI: 43.49‐47.22). After manual review of patient records including the free text, there were 712 incident VTE cases; incidence rate of 14.90 per 1000 person‐years (95% CI: 13.85‐16.02). The PPV for coded entries of VTE alone was 32.9%, and the PPV for coded entries of VTE with a coded entry of referral/hospitalization was 39.8%; this increased to 69.6% after manual review of coded clinical entries in patient records.

Conclusions

Among rivaroxaban/warfarin users in THIN, valid VTE case identification requires manual review of patient records including the free text to prevent outcome misclassification and substantial overestimation of VTE incidence rates.

Venous thromboembolism in patients with gout and the impact of hospital admission, disease duration and urate-lowering therapy

BACKGROUND

Systemic inflammatory diseases have been associated with increased risk of venous thromboembolism. We aimed to quantify the risk of venous thromboembolism in patients with gout, the most common inflammatory arthritis, and to assess how disease duration, hospital admission and urate-lowering therapy affect this risk.

METHODS

We used data from the population-representative, England-based Clinical Practice Research Datalink linked to Hospital Episode Statistics, to identify incident gout cases between 1998 and 2017. We matched cases individually to 1 control without gout on age, gender, general practice and follow-up time. We calculated absolute and relative risks of venous thromboembolism, stratified by age, gender and hospital admission. Among those with gout, we assessed the risk of venous thromboembolism by exposure to urate-lowering therapy.

RESULTS

We identified 62 234 patients with incident gout matched to 62 234 controls. Gout was associated with higher risk of venous thromboembolism compared with controls (absolute rate 37.3 [95% confidence interval (CI) 35.5-39.3] v. 27.0 [95% CI 25.5-28.9] per 10 000 person-years, adjusted hazard ratio [HR] 1.25, 95% CI 1.15-1.35). The excess risk in patients with gout, which was sustained up to a decade after diagnosis, was present during the time outside hospital stay (adjusted HR 1.30, 95% CI 1.18-1.42), but not during it (adjusted HR 1.01, 95% CI 0.83-1.24). The risk of venous thromboembolism was similar among patients prescribed versus not prescribed urate-lowering therapy (incidence rate ratio 1.04, 95% CI 0.89-1.23).

INTERPRETATION

Gout was associated with higher risk of venous thromboembolism, particularly when the patient was not in hospital and regardless of exposure to urate-lowering therapy. Although the observed excess risk may not be sufficient to warrant preventive intervention, clinical vigilance may be required when caring for these patients.

Risk of venous thromboembolism in patients with psoriatic arthritis, psoriasis and rheumatoid arthritis: a general population-based cohort study

Aims

To determine the risk of venous thromboembolism (VTE) defined as the combined endpoint of deep venous thrombosis (DVT) and pulmonary embolism (PE) among patients with psoriatic arthritis (PsA), psoriasis and rheumatoid arthritis (RA) compared with population controls.

Methods and results

A cohort study was conducted in a primary care medical record database in the UK with data from 1994-2014 among patients with PsA, RA, or psoriasis. Cox proportional hazards models were used to calculate the relative hazards for DVT, PE, and VTE. An interaction with disease modifying anti-rheumatic drugs (DMARD) was hypothesized a priori and was significant. Patients with PsA (n = 12 084), RA (n = 51 762), psoriasis (n = 194 288) and controls (n = 1 225 571) matched on general practice and start date were identified. Patients with RA (with and without a DMARD prescription) and patients with mild psoriasis had significantly elevated risks of VTE (HR 1.35, 1.29, and 1.07, respectively) after adjusting for traditional risk factors. Severe psoriasis and PsA prescribed a DMARD had an elevated but not statistically significant risk for VTE. Findings were similar for DVT. The age-and-sex-adjusted risk of PE was elevated in RA, severe psoriasis and PsA patients prescribed a DMARD.

Conclusion

While systemic inflammation is a risk factor for VTE, the risk of VTE compared with controls is different among patients with three different inflammatory disorders: RA, PsA, and psoriasis.

Elevated blood pressure and risk of aortic valve disease: a cohort analysis of 5.4 million UK adults

Aims

To test two related hypotheses that elevated blood pressure (BP) is a risk factor for aortic valve stenosis (AS) or regurgitation (AR).

Methods and results

In this cohort study of 5.4 million UK patients with no known cardiovascular disease or aortic valve disease at baseline, we investigated the relationship between BP and risk of incident AS and AR using multivariable-adjusted Cox regression models. Over a median follow-up of 9.2 years, 20 680 patients (0.38%) were diagnosed with AS and 6440 (0.12%) patients with AR. Systolic BP (SBP) was continuously related to the risk of AS and AR with no evidence of a nadir down to 115 mmHg. Each 20 mmHg increment in SBP was associated with a 41% higher risk of AS (hazard ratio 1.41, 95% confidence interval 1.38–1.45) and a 38% higher risk of AR (1.38, 1.31–1.45). Associations were stronger in younger patients but with no strong evidence for interaction by gender or body mass index. Each 10 mmHg increment in diastolic BP was associated with a 24% higher risk of AS (1.24, 1.19–1.29) but not AR (1.04, 0.97–1.11). Each 15 mmHg increment in pulse pressure was associated with a 46% greater risk of AS (1.46, 1.42–1.50) and a 53% higher risk of AR (1.53, 1.45–1.62).

Conclusion

Long-term exposure to elevated BP across its whole spectrum was associated with increased risk of AS and AR. The possible causal nature of the observed associations warrants further investigation.

Venous Thromboembolic Events in Idiopathic Inflammatory Myopathy: Occurrence and Relation to Disease Onset

OBJECTIVE

To assess the incidence of venous thromboembolic events (VTEs) in patients with idiopathic inflammatory myopathies (IIMs), to compare the incidence of VTEs in IIM to the incidence in the general population, and to identify patient categories at high risk and investigate the development of risk in relation to a diagnosis of IIM.

METHODS

Using nationwide registers, we identified a cohort of 440 individuals with newly diagnosed IIM and 4,459 individuals from the general population. Patients with IIM were diagnosed between 2005 and 2011. The start of follow-up was the date of IIM diagnosis and the corresponding date in the general population. VTE was defined as hospital care with an International Statistical Classification of Diseases and Related Health Problems, Tenth Revision code indicating VTE, with a filled prescription for anticoagulant medication. Incidence rates including 95% confidence intervals (95% CIs) were calculated, and Cox proportional hazards models were used to compare the risk of VTE in patients with IIM to the risk in the general population.

RESULTS

The incidence of VTEs was higher in patients with IIM than in the general population and was highest in patients who previously had cancer, who were ages >71 years when diagnosed with IIM, or who had dermatomyositis. The overall hazard ratio (HR) of VTE comparing the IIM cohort to the general population was 7.81 (95% CI 4.74, 12.85). The HR was highest the first year after IIM diagnosis, with HR 26.6 (95% CI 10.4, 68.0).

CONCLUSION

Patients with IIM are at increased risk of VTE compared to the general population, especially during the first year after the diagnosis. Preventive measures should be focused on patients who previously have had cancer, who are ages >71 years when diagnosed, or who have dermatomyositis.

Outcomes research on obstetric venous thromboembolism

Outcomes research on obstetric venous thromboembolism (VTE) involves a number of major challenges. While obstetric VTE, including deep vein thrombosis and pulmonary embolism, is relatively common on a population basis, diagnoses during pregnancy are relatively rare in comparison to high-risk scenarios such as orthopedic surgery. This review characterizes outcomes research on obstetric VTE with a focus on strengths, limitations, and appropriate inferences from existing research. It is divided into four sections. First, evidence regarding validity of diagnosis codes for VTE in administrative data is reviewed. Second, limitations of both clinical research and administrative-data study models are analyzed. Third, examples of high-quality obstetric VTE research from the literature and opportunities for improved research in the future are reviewed. Fourth, future directions for research are explored.

Comparing external and internal validation methods in correcting outcome misclassification bias in logistic regression: A simulation study and application to the case of postsurgical venous thromboembolism following total hip and knee arthroplasty

PURPOSE

We assessed the validity of postsurgery venous thromboembolism (VTE) diagnoses identified from administrative databases and compared Bayesian and multiple imputation (MI) approaches in correcting for outcome misclassification in logistic regression models.

METHODS

Sensitivity and specificity of postsurgery VTE among patients undergoing total hip or knee replacement (THR/TKR) were assessed against chart review in six Montreal hospitals in 2009 to 2010. Administrative data on all THR/TKR Quebec patients in 2009 to 2010 were obtained. The performance of Bayesian external, Bayesian internal, and MI approaches to correct the odds ratio (OR) of postsurgery VTE in tertiary versus community hospitals was assessed using simulations. Bayesian external approach used prior information from external sources, while Bayesian internal and MI approaches used chart review.

RESULTS

In total, 17 319 patients were included, 2136 in participating hospitals, among whom 75 had VTE in administrative data versus 81 in chart review. VTE sensitivity was 0.59 (95% confidence interval, 0.48-0.69) and specificity was 0.99 (0.98-0.99), overall. The adjusted OR of VTE in tertiary versus community hospitals was 1.35 (1.12-1.64) using administrative data, 1.45 (0.97-2.19) when MI was used for misclassification correction, and 1.53 (0.83-2.87) and 1.57 (0.39-5.24) when Bayesian internal and external approaches were used, respectively. In simulations, all three approaches reduced the OR bias and had appropriate coverage for both nondifferential and differential misclassification.

CONCLUSION

VTE identified from administrative data had low sensitivity and high specificity. The Bayesian external approach was useful to reduce outcome misclassification bias in logistic regression; however, it required accurate specification of the misclassification properties and should be used with caution.

The risk of venous thromboembolism during and after hospitalisation in patients with inflammatory bowel disease activity

BACKGROUND

Inflammatory bowel disease (IBD) increases the risk of venous thromboembolism.

AIMS

To determine when patients are at high risk of thromboembolic events, including after major surgery, and to guide timing of thromboprophylaxis.

METHODS

Each IBD patient from Clinical Practice Research Datalink, linked with Hospital Episode Statistics, was matched to up to five non-IBD patients in this cohort study. We examined their risk of thromboembolism in hospital and within 6 weeks after leaving hospital, with or without undergoing major surgery, and while ambulant. Hazard ratios were estimated using Cox regression, with adjustment for age, sex, body mass index, smoking and history of malignancy or thromboembolism.

RESULTS

Overall 23 046 IBD patients had a thromboembolic risk 1.74-times (95% CI = 1.55-1.96) higher than 106 795 non-IBD patients. Among ambulant patients, the thromboembolic risk was raised during acute (hazard ratio = 3.94, 2.79-5.57) or chronic disease activity (3.97, 2.90-5.45) but their absolute risk remained below 5/1000 person-years. The hazard ratio for thromboembolism among in-patients not undergoing major surgery was 1.13 (0.63-2.02), compared to 2.43 (1.20-4.92) among surgical patients, with a near doubling of absolute risk associated with surgery (59.5/1000 person-years, compared with 31.1 without surgery). The absolute risk remained elevated within 6 weeks after leaving hospital (18.6/1000 person-years in IBD patients after surgery).

CONCLUSIONS

IBD patients are at an increased risk of venous thromboembolism. Absolute risks are raised during active disease, when in hospital, and after leaving hospital following major surgery.

Drospirenone-Containing Oral Contraceptive Pills and the Risk of Venous Thromboembolism: An Assessment of Risk in First-Time Users and Restarters

INTRODUCTION

The effects of drospirenone-containing combined oral contraceptives (COCs) on the risk of venous thromboembolism (VTE) remain controversial due to the challenge in distinguishing between first-time users and restarters, and their different underlying VTE risks, in healthcare databases.

OBJECTIVES

The aim of this study was to describe the challenge of studying the risk of VTE among first-time users of drospirenone-containing COCs in a healthcare database and assess the risk among first-time users and restarters.

METHODS

We used data from the Clinical Practice Research Datalink to construct two cohorts. The first-time user cohort included all women aged 16-45 years who received a first ever prescription of drospirenone- or levonorgestrel-containing COCs between May 2002 and March 2015. The restarter cohort included those who were restarting a COC after a period of non-use of ≥6 months. Cox proportional hazards models adjusted for high dimensional propensity scores were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

The final cohorts included 55,139 first-time users (3582 drospirenone and 51,557 levonorgestrel) and 162,959 restarters (23,191 drospirenone and 139,768 levonorgestrel). The adjusted HR of VTE associated with drospirenone versus levonorgestrel was 3.19 (95% CI 1.12-9.08) for first-time users and 1.96 (95% CI 1.12-3.41) for restarters.

CONCLUSIONS

We found an elevated risk of VTE associated with drospirenone-containing COCs in comparison with levonorgestrel-containing COCs in both cohorts. While left truncation of healthcare databases is a concern for the identification of first-time users, the use of a more explicit cohort of restarters suggests a doubling of VTE risk with drospirenone-containing COCs.

Risk of venous thromboembolism among users of different anti-osteoporosis drugs: a population-based cohort analysis including over 200,000 participants from Spain and the UK

The venous thromboembolism risk among anti-osteoporotics is unknown. In this primary care study, the risk with other bisphosphonates [1.05 (0.94-1.18) and 0.96 (0.78-1.18)], strontium [0.90 (0.61-1.34) and 1.19 (0.82-1.74)], in the UK and Spain respectively, and denosumab [1.77 (0.25-12.66)] and teriparatide [1.27 (0.59-2.71)] in Spain, did not differ versus alendronate.

INTRODUCTION

Most of the known adverse drug reactions described for anti-osteoporosis medication (AOM) have been described in studies comparing AOM users to non-users. We aimed to compare the risk of venous thromboembolism (VTE) among incident users of different AOM compared to alendronate (first line therapy).

METHODS

Two cohort studies were performed using data from the UK (CPRD) and Spain (BIFAP) primary care records separately. All patients aged ≥ 50 years with at least 1 year of data available and a new prescription or dispensation of AOM (date for therapy initiation) during 2000-2014 (CPRD) or 2001-2013 (BIFAP) were included. Users of raloxifene/bazedoxifene were excluded from both databases. Five exposure cohorts were identified according to first treatment: (1) alendronate, (2) other bisphosphonates, (3) strontium ranelate, (4) denosumab, and (5) teriparatide. Participants were followed from the day after therapy initiation to the earliest of a treated VTE (cases), end of AOM treatment (defined by a refill gap of 180 days), switching to an alternative AOM, drop-out, death, or end of study period. Incidence rates of VTE were estimated by cohort. Adjusted hazard ratios (HR 95%CI) were estimated according to drug used.

RESULTS

Overall, 2035/159,209 (1.28%) in CPRD and 401/83,334 (0.48%) in BIFAP had VTE. Compared to alendronate, adjusted HR of VTE were 1.05 (0.94-1.18) and 0.96 (0.78-1.18) for other bisphosphonates, and 0.90 (0.61-1.34) and 1.19 (0.82-1.74) for strontium in CPRD and BIFAP, respectively; 1.77 (0.25-12.66) for denosumab and 1.27 (0.59-2.71) for teriparatide in BIFAP.

CONCLUSIONS

VTE risk during AO therapy did not differ by AOM drug use. Our data does not support an increased risk of VTE associated with strontium ranelate use in the community.

Use of Calcium Channel Blockers and Risk of Breast Cancer: A Population-based Cohort Study

BACKGROUND

Several observational studies have associated use of calcium channel blockers with an increased risk of breast cancer, but this association remains controversial. The objective of this study was to determine whether these drugs are associated with an increased risk of breast cancer overall, and to assess whether this risk varies with cumulative duration of use.

METHODS

We identified a cohort of 273,152 women newly treated with antihypertensive drugs between 1 January 1995 and 31 December 2009, followed until 31 December 2010, using the UK Clinical Practice Research Datalink. We treated calcium channel blocker use as a time-varying variable, and lagged exposure by 1 year for latency considerations and to minimize reverse causality. We used time-dependent Cox proportional hazards models to estimate adjusted hazard ratios with 95% confidence intervals of incident breast cancer associated with use of calcium channel blockers overall and by cumulative duration of use (<5, 5-10, and ≥10 years).

RESULTS

During 1,567,104 person-years of follow-up, 4,520 women were newly diagnosed with breast cancer (incidence rate: 2.9 per 1,000 per year). Compared with use of other antihypertensive drugs, use of calcium channel blockers was not associated with increased risk of breast cancer overall (hazard ratio: 0.97, 95% confidence interval: 0.91, 1.03). Similarly, there was no evidence of a duration-response relationship in terms of cumulative duration of use (P trend = 0.26).

CONCLUSIONS

The results of this large population-based study indicate that long-term use of calcium channel blockers is not associated with an increased risk of breast cancer.

Epidemiology of first and recurrent venous thromboembolism in patients with active cancer

Population studies on the incidence of venous thromboembolism (VTE) in patients with active cancer are limited. An observational cohort study was undertaken to estimate the incidence of first and recurrent VTE. The source population consisted of all patients in the UK Clinical Practice Research Datalink, with additional information on hospitalisation and cause of death, between 2001 and 2011. A cancer-related clinical diagnosis or therapy within the 90 days before or after a VTE constituted an active-cancer-associated VTE. Incidence rates of first VTE among patients with active cancer and incidence rates of recurrent VTE during the 10-year observational period after a first VTE event were estimated. Incidence rates of all-cause mortality and age- and gender-specific mortality were also calculated. There were 6,592 active-cancer-associated VTEs with a total of 112,738 cancer-associated person-years of observation. The incidence rate of first VTE in patients with active cancer was 5.8 (95 % confidence interval 5.7–6.0) per 100 person-years. A first VTE recurrence was observed in 591 patients. The overall incidence rate for recurrence was 9.6 (95 % confidence interval 8.8–10.4) per 100 person-years, with a peak at 22.1 in the first six months. Recurrence rates were similar after initial pulmonary embolism and after initial deep-vein thrombosis. The mortality risk after VTE was considerable, with 64.5 % mortality after one year and 88.1 % after 10 years. VTE in patients with active cancer is common and associated with high recurrence and mortality rates. Efforts are needed to prevent VTE and reduce recurrence, especially in the first year after VTE diagnosis.

Supplementary Material to this article is available online at www.thrombosis-online.com.

The concurrent use of antithrombotic therapies and the risk of bleeding in patients with atrial fibrillation

Patients with atrial fibrillation (AF) often receive, in addition to warfarin, antithrombotic drugs to manage other comorbid conditions. To date, few population-based studies have quantified the bleeding risk associated with the concurrent use of these therapies. The United Kingdom General Practice Research Database was used to identify a cohort of 70,760 patients newly-diagnosed with AF between 1993 and 2008. A nested case-control analysis was conducted within that cohort, and conditional logistic regression was used to estimate adjusted rate ratios (RRs) of bleeding associated with current use of warfarin, aspirin, and clopidogrel in single therapy, as well as in dual and triple therapy, as compared with non-use of any therapy. A total of 10,850 patients experienced a bleeding event during follow-up. In single therapy, warfarin was associated with the highest increased risk (RR: 2.08, 95% confidence interval [CI]: 1.95–2.23), followed by clopidogrel (RR: 1.57, 95% CI: 1.37–1.81) and aspirin (RR: 1.25, 95% CI: 1.17–1.34). In dual therapy, combinations containing warfarin were associated with a higher increased risk (warfarin-aspirin: RR: 2.87, 95% CI: 2.58–3.19, and warfarin-clopidogrel: RR: 2.74, 95% CI: 2.14–3.51), than those not containing warfarin (aspirin-clopidogrel: RR: 1.68, 95% CI: 1.44–1.97). Triple therapy of warfarin-aspirin-clopidogrel was associated with the highest increased risk (RR: 3.75, 95% CI: 2.71–5.19). This large population-based study suggests that while all antithrombotic therapies are associated with an elevated risk of bleeding, the risks increase in an additive fashion with dual and triple therapy, particularly in combinations containing warfarin.

Venous thromboembolism and mortality in breast cancer: cohort study with systematic review and meta-analysis

BACKGROUND

Breast cancer patients are at an increased risk of venous thromboembolism (VTE). However, current evidence as to whether VTE increases the risk of mortality in breast cancer patients is conflicting. We present data from a large cohort of patients from the UK and pool these with previous data from a systematic review.

METHODS

Using the Clinical Practice Research Datalink (CPRD) dataset, we identified a cohort of 13,202 breast cancer patients, of whom 611 were diagnosed with VTE between 1997 and 2006 and 12,591 did not develop VTE. Hazard ratios (HR) were used to compare mortality between the two groups. These were then pooled with existing data on this topic identified via a search of the MEDLINE and EMBASE databases (until January 2015) using a random-effects meta-analysis.

RESULTS

Within the CPRD, VTE was associated with increased mortality when treated as a time-varying covariate (HR = 2.42; 95% CI, 2.13-2.75), however, when patients were permanently classed as having VTE based on presence of a VTE event within 6 months of cancer diagnosis, no increased risk was observed (HR = 1.22; 0.93-1.60). The pooled HR from seven studies using the second approach was 1.69 (1.12-2.55), with no effect seen when restricted to studies which adjusted for key covariates.

CONCLUSION

A large HR for VTE in the time-varying covariate analysis reflects the known short-term mortality following a VTE. When breast cancer patients are fortunate to survive the initial VTE, the influence on longer-term mortality is less certain.

Elevated blood pressure and risk of mitral regurgitation: A longitudinal cohort study of 5.5 million United Kingdom adults

BACKGROUND

Mitral regurgitation in people without prior cardiac disease is considered a degenerative disease with no established risk factors for its prevention. We aimed to test the hypothesis that elevated systolic blood pressure (SBP) across its usual spectrum is associated with higher risk of mitral regurgitation.

METHODS AND FINDINGS

We used linked electronic health records from the United Kingdom Clinical Practice Research Datalink (CPRD) from 1 January 1990 to 31 December 2015. CPRD covers approximately 7% of the current UK population and is broadly representative of the population by age, sex, and ethnicity. About 5.5 million UK patients with no known cardiovascular or valve disease at baseline were included in this cohort study. We investigated the relationship between blood pressure (BP) and risk of mitral regurgitation using Cox regression models. Our primary exposure variable was SBP and our primary outcome was incident reports of mitral regurgitation, which were identified from hospital discharge reports or primary care records. Of the 5,553,984 patients in the CPRD that met our inclusion criteria, during the 10-year follow-up period, 28,655 (0.52%) were diagnosed with mitral regurgitation and a further 1,262 (0.02%) were diagnosed with mitral stenosis. SBP was continuously related to the risk of mitral regurgitation with no evidence of a nadir down to 115 mmHg (p < 0.001). Each 20 mmHg increment in SBP was associated with a 26% higher risk of mitral regurgitation (hazard ratio [HR] 1.26; CI 1.23, 1.29). The observed association was partially mediated by diseases affecting the left ventricle during follow-up (myocardial infarction [MI], ischaemic heart disease [IHD], cardiomyopathy, and heart failure). However, the percentage of excess risk mediated (PERM) by these proximate causes of secondary mitral regurgitation was only 13% (CI 6.1%, 20%), and accounting for them had little effect on the long-term association between SBP and mitral regurgitation (mediator-adjusted HR 1.22; CI 1.20, 1.25; p < 0.001). Associations were similar for each 10 mmHg increment in diastolic blood pressure (DBP) (p < 0.001) or each 15 mmHg increment in pulse pressure (PP) (p < 0.001). By contrast, there was no association between SBP and risk of mitral stenosis (HR per 20 mmHg higher SBP 1.03; CI 0.93, 1.14; p = 0.58). These analyses are based on routinely collected data from health records which may be sensitive to measurement errors, and the observed associations may not be generalizable to less severe and subclinical cases of mitral regurgitation.

CONCLUSIONS

Long-term exposure to elevated BP across its whole spectrum is associated with an increased risk of primary and secondary mitral regurgitation. These findings suggest that BP control may be of importance in the prevention of mitral regurgitation.

Venous thromboembolism in adults screened for sickle cell trait: a population-based cohort study with nested case-control analysis

OBJECTIVE

To determine whether sickle cell carriers ('sickle cell trait') have an increased risk of venous thromboembolism (VTE).

DESIGN

Cohort study with nested case-control analysis.

SETTING

General population with data from 609 UK general practices in the Clinical Practice Research Datalink (CPRD).

PARTICIPANTS

All individuals registered with a CPRD general practice between 1998 and 2013, with a medical record of screening for sickle cell between 18 and 75 years of age.

MAIN OUTCOMES MEASURES

Incidence of VTE per 10 000 person-years (PY) among sickle cell carriers and non-carriers; and adjusted OR for VTE among sickle cell carriers compared with non-carriers.

RESULTS

We included 30 424 individuals screened for sickle cell, with a follow-up time of 179 503 PY, identifying 55 VTEs in 6758 sickle cell carriers and 125 VTEs in 23 666 non-carriers. VTE incidence among sickle cell carriers (14.9/10 000 PY; 95% CI 11.4 to 19.4) was significantly higher than non-carriers (8.8/10 000 PY; 95% CI 7.4 to 10.4). Restricting analysis to confirmed non-carriers was non-significant, but performed on a small sample. In the case-control analysis (180 cases matched to 1775 controls by age and gender), sickle cell carriers remained at increased risk of VTE after adjusting for body mass index, pregnancy, smoking status and ethnicity (OR 1.78, 95% CI 1.18 to 2.69, p=0.006), with the greatest risk for pulmonary embolism (PE) (OR 2.27, 95% CI 1.17 to 4.39, p=0.011).

CONCLUSIONS

Although absolute numbers are small, in a general population screened for sickle cell, carriers have a higher incidence and risk of VTE, particularly PE, than non-carriers. Clinicians should be aware of this elevated risk in the clinical care of sickle cell carriers, or when discussing carrier screening, and explicitly attend to modifiable risk factors for VTE in these individuals. More complete primary care coding of carrier status could improve analysis.

Development and validation of risk prediction model for venous thromboembolism in postpartum women: multinational cohort study

OBJECTIVE

 To develop and validate a risk prediction model for venous thromboembolism in the first six weeks after delivery (early postpartum).

DESIGN

 Cohort study.

SETTING

 Records from England based Clinical Practice Research Datalink (CPRD) linked to Hospital Episode Statistics (HES) and data from Sweden based registry.

PARTICIPANTS

 All pregnant women registered with CPRD-HES linked data between 1997 and 2014 and Swedish medical birth registry between 2005 and 2011 with postpartum follow-up.

MAIN OUTCOME MEASURE

 Multivariable logistic regression analysis was used to develop a risk prediction model for postpartum venous thromboembolism based on the English data, which was externally validated in the Swedish data.

RESULTS

 433 353 deliveries were identified in the English cohort and 662 387 in the Swedish cohort. The absolute rate of venous thromboembolism was 7.2 per 10 000 deliveries in the English cohort and 7.9 per 10 000 in the Swedish cohort. Emergency caesarean delivery, stillbirth, varicose veins, pre-eclampsia/eclampsia, postpartum infection, and comorbidities were the strongest predictors of venous thromboembolism in the final multivariable model. Discrimination of the model was similar in both cohorts, with a C statistic above 0.70, with excellent calibration of observed and predicted risks. The model identified more venous thromboembolism events than the existing national English (sensitivity 68% v 63%) and Swedish guidelines (30% v 21%) at similar thresholds.

CONCLUSION

 A new prediction model that quantifies absolute risk of postpartum venous thromboembolism has been developed and externally validated. It is based on clinical variables that are available in many developed countries at the point of delivery and could serve as the basis for real time decisions on obstetric thromboprophylaxis.

Testosterone treatment and risk of venous thromboembolism: population based case-control study

OBJECTIVE

 To determine the risk of venous thromboembolism associated with use of testosterone treatment in men, focusing particularly on the timing of the risk.

DESIGN

 Population based case-control study SETTING:  370 general practices in UK primary care with linked hospital discharge diagnoses and in-hospital procedures and information on all cause mortality.

PARTICIPANTS

 19 215 patients with confirmed venous thromboembolism (comprising deep venous thrombosis and pulmonary embolism) and 909 530 age matched controls from source population including more than 2.22 million men between January 2001 and May 2013.

EXPOSURE OF INTEREST

 Three mutually exclusive testosterone exposure groups were identified: current treatment, recent (but not current) treatment, and no treatment in the previous two years. Current treatment was subdivided into duration of more or less than six months.

MAIN OUTCOME MEASURE

 Rate ratios of venous thromboembolism in association with current testosterone treatment compared with no treatment were estimated using conditional logistic regression and adjusted for comorbidities and all matching factors.

RESULTS

 The adjusted rate ratio of venous thromboembolism was 1.25 (95% confidence interval 0.94 to 1.66) for current versus no testosterone treatment. In the first six months of testosterone treatment, the rate ratio of venous thromboembolism was 1.63 (1.12 to 2.37), corresponding to 10.0 (1.9 to 21.6) additional venous thromboembolisms above the base rate of 15.8 per 10 000 person years. The rate ratio after more than six months' treatment was 1.00 (0.68 to 1.47), and after treatment cessation it was 0.68 (0.43 to 1.07). Increased rate ratios within the first six months of treatment were observed in all strata: the rate ratio was 1.52 (0.94 to 2.46) for patients with pathological hypogonadism and 1.88 (1.02 to 3.45) for those without it, and 1.41 (0.82 to 2.41) for those with a known risk factor for venous thromboembolism and 1.91 (1.13 to 3.23) for those without one.

CONCLUSIONS

 Starting testosterone treatment was associated with an increased risk of venous thromboembolism, which peaked within six months and declined thereafter.

Risk of venous thromboembolism in people with lung cancer: a cohort study using linked UK healthcare data

Background:

Venous thromboembolism (VTE) is a potentially preventable cause of death in people with lung cancer. Identification of those most at risk and high-risk periods may provide the opportunity for better targeted intervention.

Methods:

We conducted a cohort study using the Clinical Practice Research Datalink linked to Hospital Episode Statistics and Cancer Registry data. Our cohort comprises 10 598 people with lung cancer diagnosed between 1997 and 2006 with follow-up continuing to the end of 2010. Cox regression analysis was performed to determine which demographic, tumour and treatment-related factors (time-varying effects of chemotherapy and surgery) independently affected VTE risk. We also determined the effect of a VTE diagnosis on the survival of people with lung cancer.

Results:

People with lung cancer had an overall VTE incidence of 39.2 per 1000 person-years (95% confidence interval (CI), 35.4–43.5), though rates varied depending on the patient group and treatment course. Independent factors associated with increased VTE risk were metastatic disease (hazard ratio (HR)=1.9, CI 1.2–3.0 vs local disease); adenocarcinoma subtype (HR=2.0, CI 1.5–2.7, vs squamous cell; chemotherapy administration (HR=2.1, CI 1.4–3.0 vs outside chemotherapy courses); and diagnosis via emergency hospital admission (HR=1.7, CI 1.2–2.3 vs other routes to diagnosis). Patients with VTE had an approximately 50% higher risk of mortality than those without VTE.

Conclusions:

People with lung cancer have especially high risk of VTE if they have advanced disease, adenocarcinoma or are undergoing chemotherapy. The presence of VTE is an independent risk factor for death.

COPD disease severity and the risk of venous thromboembolic events: a matched case-control study

BACKGROUND

It is generally accepted that people with chronic obstructive pulmonary disease (COPD) are at increased risk of vascular disease, including venous thromboembolism (VTE). While it is plausible that the risk of arterial and venous thrombotic events is greater still in certain subgroups of patients with COPD, such as those with more severe airflow limitation or more frequent exacerbations, these associations, in particular those between venous events and COPD severity or exacerbation frequency, remain largely untested in large population cohorts.

METHODS

A total of 3,594 patients with COPD with a first VTE event recorded during January 1, 2004 to December 31, 2013, were identified from the Clinical Practice Research Datalink dataset and matched on age, sex, and general practitioner practice (1:3) to patients with COPD with no history of VTE (n=10,782). COPD severity was staged by degree of airflow limitation (ie, GOLD stage) and by COPD medication history. Frequent exacerbators were defined as patients with COPD with ≥ 2 exacerbations in the 12-month period prior to their VTE event (for cases) or their selection as a control (for controls). Conditional logistic regression was used to estimate the association between disease severity or exacerbation frequency and VTE.

RESULTS

After additional adjustment for nonmatching confounders, including body mass index, smoking, and heart-related comorbidities, there was evidence for an association between increased disease severity and VTE when severity was measured either in terms of lung function impairment (odds ratio [OR]moderate:mild =1.16; 95% confidence intervals [CIs] =1.03, 1.32) or medication usage (ORsevere:mild/moderate =1.17; 95% CIs =1.06, 1.26). However, there was no evidence to suggest that frequent exacerbators were at greater risk of VTE compared with infrequent exacerbators (OR =1.06; 95% CIs =0.97, 1.15).

CONCLUSION

COPD severity defined by airflow limitation or medication usage, but not exacerbation frequency, appears to be associated with VTE events in people with COPD. This finding highlights the disconnect between disease activity and severity in COPD.

Total joint arthroplasty and the risk of myocardial infarction: a general population, propensity score-matched cohort study

OBJECTIVE

To replicate recent findings indicating that total knee arthroplasty (TKA) or total hip arthroplasty (THA) surgery will substantially reduce the risk of serious cardiovascular events among patients with osteoarthritis.

METHODS

A time-stratified, propensity score-matched cohort study was conducted to assess the incidence of myocardial infarction (MI) in a UK general population. The study population included individuals ages ≥50 years who had a UK National Health Service READ code diagnosis of knee osteoarthritis (to evaluate TKA) or hip osteoarthritis (to evaluate THA) between January 2000 and December 2012.

RESULTS

Among the patients who underwent TKA and their matched non-TKA control subjects (each n = 13,849), 306 patients and 286 control subjects developed MI during the followup. During the first postoperative month, the risk of MI was substantially increased among the TKA group compared with the non-TKA group (hazard ratio [HR] 8.75, 95% confidence interval [95% CI] 3.11-24.62), and then gradually declined during the subsequent followup. The HR for the risk of MI over the entire followup was 0.98 (95% CI 0.82-1.18). The corresponding HRs for the risk of MI in those who had undergone THA compared with the non-THA group (each n = 6,063) were 4.33 (95% CI 1.24-15.21) in the first postoperative month and 0.87 (95% CI 0.66-1.15) overall. In analyses using venous thromboembolism as a positive control outcome, both the first month and overall HRs for the risk of venous thromboembolism were substantially increased in both the TKA and THA groups.

CONCLUSION

These findings provide the first general population-based evidence to indicate that TKA and THA among osteoarthritis patients are associated with a substantially increased risk of MI during the immediate postoperative period. However, the overall long-term impact of these surgeries was null, unlike the risk of venous thromboembolism, which remained elevated years after patients had undergone the procedure.

The Impact of the Choice of Data Source in Record Linkage Studies Estimating Mortality in Venous Thromboembolism

Linked electronic healthcare databases are increasingly being used in observational research. The objective of this study was to investigate the impact of the choice of data source in estimating mortality following VTE, with a secondary aim to investigate the influence of the denominator definition. We used the UK Clinical Practice Research Datalink (CPRD) to identify patients aged 18+ with venous thromboembolism (VTE). Multiple cohorts were identified in order to assess how mortality rates differed with a range of data sources. For each of the cohorts, incidence rates per 1,000 person years (/1000py) and relative rates (RRs) of all-cause mortality were calculated. The lowest mortality rate was found when only primary care data were used for both the exposure (VTE) and the outcome (death) (108.4/1000py). The highest mortality rate was found for patients diagnosed in secondary care (237.2/1000py). When linked primary and secondary care data were included for eligible patients and for the overlapping period of data collection, a mortality rate of 173.2/1000py was found. Sensitivity analyses varying the denominator definition provided a range of results (140.6–164.3/1000py). The relative rates of mortality by gender and age were comparable across all cohorts. Depending on the choice of data source, the population studied may be different. This may have substantial impact on the main findings, in particular on incidence rates of mortality following VTE.

Risk of symptomatic venous thromboembolism following emergency appendicectomy in adults

Background

Appendicectomy is the commonest intra-abdominal emergency surgical procedure, and little is known regarding the magnitude and timing of the risk of venous thromboembolism (VTE) after surgery. This study aimed to determine absolute and relative rates of symptomatic VTE following emergency appendicectomy.

Methods

A cohort study was undertaken using linked primary (Clinical Practice Research Datalink) and secondary (Hospital Episode Statistics) care data of patients who had undergone emergency appendicectomy from 2001 to 2011. Crude rates and adjusted incidence rate ratios (IRRs) for VTE were calculated using Poisson regression, compared with baseline risk in the year before appendicectomy.

Results

A total of 13 441 patients were identified, of whom 56 (0·4 per cent) had a VTE in the first year after surgery. The absolute rate of VTE was highest during the in-hospital period, with a rate of 91·29 per 1000 person-years, which was greatest in those with a length of stay of 7 days or more (267·12 per 1000 person-years). This risk remained high after discharge, with a 19·1- and 6·6-fold increased risk of VTE in the first and second months respectively after discharge, compared with the year before appendicectomy (adjusted IRR: month 1, 19·09 (95 per cent c.i. 9·56 to 38·12); month 2, 6·56 (2·62 to 16·44)).

Conclusion

The risk of symptomatic VTE following appendicectomy is relatively high during the in-hospital admission and remains increased after discharge. Trials of extended thromboprophylaxis are warranted in patients at particularly high risk.

Risk of Post-Discharge Venous Thromboembolism and Associated Mortality in General Surgery: A Population-Based Cohort Study Using Linked Hospital and Primary Care Data in England

Background

Trends towards day case surgery and enhanced recovery mean that postoperative venous thromboembolism (VTE) may increasingly arise after hospital discharge. However, hospital data alone are unable to capture adverse events that occur outside of the hospital setting. The National Institute for Health and Care Excellence has suggested the use of primary care data to quantify hospital care-related VTE. Data in surgical patients using these resources is lacking. The aim of this study was to measure VTE risk and associated mortality in general surgery using linked primary care and hospital databases, to improve our understanding of harm from VTE that arises beyond hospital stay.

Methods

This was a longitudinal cohort study using nationally linked primary care (Clinical Practice Research Datalink, CPRD), hospital administrative (Hospital Episodes Statistics, HES), population statistics (Office of National Statistics, ONS) and National Cancer Intelligence Network databases. Routinely collected information was used to quantify 90-day in-hospital VTE, 90-day post-discharge VTE and 90-day mortality in adults undergoing one of twelve general surgical procedures between 1st April 1997 and 31st March 2012. The earliest postoperative recording of deep vein thrombosis or pulmonary embolism in CPRD, HES and ONS was counted in each patient. Covariates from multiple datasets were combined to derive detailed prediction models for VTE and mortality. Limitation included the capture of VTE presenting to healthcare only and the lack of information on adherence to pharmacological thromboprophylaxis as there was no data linkage to hospital pharmacy records.

Results

There were 981 VTE events captured within 90 days of surgery in 168005 procedures (23.7/1000 patient-years). Overall, primary care data increased the detection of postoperative VTE by a factor of 1.38 (981/710) when compared with using HES and ONS only. Total VTE rates ranged between 3.2/1000 patient-years in haemorrhoidectomy to 118.3/1000 patient-years in esophagogastric resection. Predictors of VTE included emergency surgery (OR = 1.91 95%CI 1.60–2.28, p<0.001), age (OR = 1.02 95%CI 1.02–1.03, p<0.001), body mass index (OR = 1.03 95%CI 1.01–1.04, p<0.001), previous VTE (OR = 8.07 95%CI 6.61–9.83, p<0.001), length of stay (OR = 1.00 95%CI 1.00–1.00, p = 0.007) and cancer stages II (OR = 1.38 95%CI 1.03–1.87, p = 0.033), III (OR = 1.50 95%CI 1.11–2.01, p = 0.008) and IV (OR = 1.63 95%CI 1.03–2.59, p = 0.038). Major organ resections had the greatest odds of VTE when adjusted for other risk factors including length of hospital stay. Post-discharge VTE accounted for 64.8% (636/981) of all recorded VTE. In-hospital VTE (165.4/1000 patient-years) was recorded more frequently than post-discharge VTE (16.2/1000 patient-years). Both in-hospital (OR = 2.07 95%CI 1.51–2.85, p<0.001) and post-discharge (OR = 4.03 95%CI 2.95–5.51, p<0.001) VTE independently predicted 90-day mortality. In patients who died and VTE was recorded on HES or CPRD (n = 56), VTE was one of the causes of death in 37.5% (21/56) of cases.

Conclusions

A large proportion of postoperative VTE was detected in primary care. Evaluation of linked databases was a useful way of measuring postoperative VTE at population level. These resources identified a significant association between post-discharge VTE and mortality in general surgery.

When are breast cancer patients at highest risk of venous thromboembolism? A cohort study using English health care data

Patients with breast cancer are at increased risk of venous thromboembolism (VTE), particularly in the peridiagnosis period. However, no previous epidemiologic studies have investigated the relative impact of breast cancer treatments in a time-dependent manner. We aimed to determine the impact of breast cancer stage, biology, and treatment on the absolute and relative risks of VTE by using several recently linked data sources from England. Our cohort comprised 13,202 patients with breast cancer from the Clinical Practice Research Datalink (linked to Hospital Episode Statistics and Cancer Registry data) diagnosed between 1997 and 2006 with follow-up continuing to the end of 2010. Cox regression analysis was performed to determine which demographic, treatment-related, and biological factors independently affected VTE risk. Women had an annual VTE incidence of 6% while receiving chemotherapy which was 10.8-fold higher (95% confidence interval [CI], 8.2-14.4; absolute rate [AR], 59.6 per 1000 person-years) than that in women who did not receive chemotherapy. After surgery, the risk was significantly increased in the first month (hazard ratio [HR], 2.2; 95% CI, 1.4-3.4; AR, 23.5; reference group, no surgery), but the risk was not increased after the first month. Risk of VTE was noticeably higher in the 3 months after initiation of tamoxifen compared with the risk before therapy (HR, 5.5; 95% CI, 2.3-12.7; AR, 24.1); however, initiating therapy with aromatase inhibitors was not associated with VTE (HR, 0.8; 95% CI, 0.5-1.4; AR, 28.3). In conclusion, women receiving chemotherapy for breast cancer have a clinically important risk of VTE, whereas an increased risk of VTE immediately after endocrine therapy is restricted to tamoxifen.

Defining venous thromboembolism and measuring its incidence using Swedish health registries: a nationwide pregnancy cohort study

OBJECTIVE

To accurately define venous thromboembolism (VTE) in the routinely collected Swedish health registers and quantify its incidence in and around pregnancy.

STUDY DESIGN

Cohort study using data from the Swedish Medical Birth Registry (MBR) linked to the National Patient Registry (NPR) and the Swedish Prescribed Drug Register (PDR).

SETTING

Secondary care centres, Sweden.

PARTICIPANT

509,198 women aged 15-44 years who had one or more pregnancies resulting in a live birth or stillbirth between 2005 and 2011.

MAIN OUTCOME MEASURE

To estimate the incidence rate (IR) of VTE in and around pregnancy using various VTE definitions allowing direct comparison with other countries.

RESULTS

The rate of VTE varied based on the VTE definition. We found that 43% of cases first recorded as outpatient were not accompanied by anticoagulant prescriptions, whereas this proportion was much lower than those cases first recorded in the inpatient register (9%). Using our most inclusive VTE definition, we observed higher rates of VTE compared with previously published data using similar methodology. These reduced by 31% (IR=142/100,000 person-years; 95% CI 132 to 153) and 22% (IR=331/100,000 person-years; 95% CI 304 to 361) during the antepartum and postpartum periods, respectively, using a restrictive VTE definition that required anticoagulant prescriptions associated with diagnosis, which were more in line with the existing literature.

CONCLUSIONS

We found that including VTE codes without treatment confirmation risks the inclusion of false-positive cases. When defining VTE using the NPR, anticoagulant prescription information should therefore be considered particularly for cases recorded in an outpatient setting.

Risk of venous thromboembolism in children after general surgery

BACKGROUND/PURPOSE

The purpose of the study was to determine absolute and relative rates of venous thromboembolism (VTE) following general surgical procedures in children compared to the general population.

METHODS

We analyzed data from all patients under the age of 18years in the Clinical Practice Research Datalink, linked to Hospital Episode Statistics from England (2001-2011) undergoing a general surgical procedure and population controls. Crude rates of VTE and adjusted hazard ratios were calculated using Cox regression.

RESULTS

We identified 15,637 children who had a surgical procedure with 161,594 controls. Six children undergoing surgery had a VTE diagnosed in the year after compared to five children in the population cohort. The overall rate of VTE following surgery was 0.4 per 1000 person years (pyrs) (95% confidence interval [CI] 0.15-0.88) compared to 0.04 per 1000 pyrs (95% CI 0.02-0.09) in the population cohort. This represented a 9 fold increase in risk compared to the population cohort (adjusted hazard ratio [HR] 8.80; 95% CI 2.59-29.94).

CONCLUSIONS

Children are at increased risk for VTE following general surgical procedures compared to the general population however the absolute risk is small and given this the benefits of thromboprophylaxis need to be balanced against the risk of complications following its use.

Variation in the risk of venous thromboembolism following colectomy

Background

Guidelines recommend extended thromboprophylaxis following colectomy for malignant disease, but not for non-malignant disease. The aim of this study was to determine absolute and relative rates of venous thromboembolism (VTE) following colectomy by indication, admission type and time after surgery.

Methods

A cohort study of patients undergoing colectomy in England was undertaken using linked primary (Clinical Practice Research Datalink) and secondary (Hospital Episode Statistics) care data (2001–2011). Crude rates and adjusted hazard ratios (HRs) were calculated for the risk of first VTE following colectomy using Cox regression analysis.

Results

Some 12 388 patients were identified; 312 (2·5 per cent) developed VTE after surgery, giving a rate of 29·59 (95 per cent c.i. 26·48 to 33·06) per 1000 person-years in the first year after surgery. Overall rates were 2·2-fold higher (adjusted HR 2·23, 95 per cent c.i. 1·76 to 2·50) for emergency compared with elective admissions (39·44 versus 25·78 per 1000 person-years respectively). Rates of VTE were 2·8-fold higher in patients with malignant disease versus those with non-malignant disease (adjusted HR 2·84, 2·04 to 3·94). The rate of VTE was highest in the first month after emergency surgery, and declined from 121·68 per 1000 person-years in the first month to 25·65 per 1000 person-years during the rest of the follow-up interval. Crude rates of VTE were similar for malignant and non-malignant disease (114·76 versus 120·98 per 1000 person-years respectively) during the first month after emergency surgery.

Conclusion

Patients undergoing emergency colectomy for non-malignant disease have a similar risk of VTE as patients with malignant disease in the first month after surgery.

Use of combined oral contraceptives and risk of venous thromboembolism: nested case-control studies using the QResearch and CPRD databases

OBJECTIVE

To investigate the association between use of combined oral contraceptives and risk of venous thromboembolism, taking the type of progestogen into account.

DESIGN

Two nested case-control studies.

SETTING

General practices in the United Kingdom contributing to the Clinical Practice Research Datalink (CPRD; 618 practices) and QResearch primary care database (722 practices).

PARTICIPANTS

Women aged 15-49 years with a first diagnosis of venous thromboembolism in 2001-13, each matched with up to five controls by age, practice, and calendar year.

MAIN OUTCOME MEASURES

Odds ratios for incident venous thromboembolism and use of combined oral contraceptives in the previous year, adjusted for smoking status, alcohol consumption, ethnic group, body mass index, comorbidities, and other contraceptive drugs. Results were combined across the two datasets.

RESULTS

5062 cases of venous thromboembolism from CPRD and 5500 from QResearch were analysed. Current exposure to any combined oral contraceptive was associated with an increased risk of venous thromboembolism (adjusted odds ratio 2.97, 95% confidence interval 2.78 to 3.17) compared with no exposure in the previous year. Corresponding risks associated with current exposure to desogestrel (4.28, 3.66 to 5.01), gestodene (3.64, 3.00 to 4.43), drospirenone (4.12, 3.43 to 4.96), and cyproterone (4.27, 3.57 to 5.11) were significantly higher than those for second generation contraceptives levonorgestrel (2.38, 2.18 to 2.59) and norethisterone (2.56, 2.15 to 3.06), and for norgestimate (2.53, 2.17 to 2.96). The number of extra cases of venous thromboembolism per year per 10,000 treated women was lowest for levonorgestrel (6, 95% confidence interval 5 to 7) and norgestimate (6, 5 to 8), and highest for desogestrel (14, 11 to 17) and cyproterone (14, 11 to 17).

CONCLUSIONS

In these population based, case-control studies using two large primary care databases, risks of venous thromboembolism associated with combined oral contraceptives were, with the exception of norgestimate, higher for newer drug preparations than for second generation drugs.

Concurrent use of statins and hormone therapy and risk of venous thromboembolism in postmenopausal women: a population-based case-control study

OBJECTIVE

Statins and hormone therapy (HT), often used concurrently in postmenopausal women, have antagonist effects on the risk of venous thromboembolism (VTE). This study aims to determine whether statins attenuate the increased VTE risk associated with HT.

METHODS

We conducted a nested case-control study within a population-based cohort of women aged 50 to 79 years between January 1, 1987 and March 1, 2008, who were identified from the UK General Practice Research Database. Cases of VTE occurring during follow-up were identified and each matched with up to 10 controls from the cohort. Odds ratios (ORs) for the effects of concurrent HT and statin use on the risk of VTE were estimated using conditional logistic regression with interaction terms.

RESULTS

The cohort included 955,582 postmenopausal women, with 23,505 cases of VTE matched with 231,562 controls. Regardless of any HT use, current use of statins was associated with a decreased risk of VTE (OR, 0.83; 95% CI, 0.78-0.87). The interaction between statin use and HT use was of borderline significance (P = 0.053). Consequently, among nonusers of statins, the risk of VTE was elevated with current use of oral estrogen and progestogen combinations (OR, 1.55; 95% CI, 1.45-1.66) but this risk was not elevated among users of statins (OR, 0.98; 95% CI, 0.56-1.73). There was no such modification of the OR with statins and other HT types and formulations.

CONCLUSIONS

Statins could potentially attenuate the increased risk associated with HT combinations of oral estrogens and progestogens. This observation needs further confirmation in other large cohorts.