Evaluation of a screening protocol to exclude the diagnosis of deep venous thrombosis among emergency department patients

Optimizing resource allocation: Cost-effectiveness of specified D-dimer cut-offs in cancer patients with suspected venous thromboembolism

An accurate diagnosis of venous thromboembolism (VTE) is crucial, given the potential for high mortality in undetected cases. Strategic D-dimer testing may aid in identifying low-risk patients, preventing overdiagnosis and reducing imaging costs. We conducted a retrospective, comparative analysis to assess the potential cost savings that could be achieved by adopting different approaches to determine the most effective D-dimer cut-off value in cancer patients with suspected VTE, compared to the commonly used rule-out cut-off level of 0.5 mg/L. The study included 526 patients (median age 65, IQR 55-75) with a confirmed cancer diagnosis who underwent D-dimer testing. Among these patients, the VTE prevalence was 29% (n = 152). Each diagnostic strategy's sensitivity, specificity, negative likelihood ratio (NLR), as well as positive likelihood ratio (PLR), and the proportion of patients exhibiting a negative D-dimer test result, were calculated. The diagnostic strategy that demonstrated the best balance between specificity, sensitivity, NLR, and PLR, utilized an inverse age-specific cut-off level for D-dimer [0.5 + (66-age) × 0.01 mg/L]. This method yielded a PLR of 2.9 at a very low NLR for the exclusion of VTE. We observed a significant cost reduction of 4.6% and 1.0% for PE and DVT, respectively. The utilization of an age-adjusted cut-off [patient's age × 0.01 mg/L] resulted in the highest cost savings, reaching 8.1% for PE and 3.4% for DVT. Using specified D-dimer cut-offs in the diagnosis of VTE could improve economics, considering the limited occurrence of confirmed cases among patients with suspected VTE.

Cost-effectiveness of diagnostic strategies for venous thromboembolism: a systematic review

Guideline developers consider cost-effectiveness evidence in decision making to determine value for money. This consideration in the guideline development process can be informed either by formal and dedicated economic evaluations or by systematic reviews of existing studies. To inform the American Society of Hematology guideline on the diagnosis of venous thromboembolism (VTE), we conducted a systematic review focused on the cost-effectiveness of diagnostic strategies for VTE within the guideline scope. We systematically searched Medline (Ovid), Embase (Ovid), National Health Service Economic Evaluation Database, and the Cost-effectiveness Analysis Registry; summarized; and critically appraised the economic evidence on diagnostic strategies for VTE. We identified 49 studies that met our inclusion criteria, with 26 on pulmonary embolism (PE) and 24 on deep vein thrombosis (DVT). For the diagnosis of PE, strategies including d-dimer to exclude PE were cost-effective compared with strategies without d-dimer testing. The cost-effectiveness of computed tomography pulmonary angiogram (CTPA) in relation to ventilation-perfusion (V/Q) scan was inconclusive. CTPA or V/Q scan following ultrasound or d-dimer results could be cost-effective or even cost saving. For DVT, studies supporting strategies with d-dimer and/or ultrasound were cost-effective, supporting the recommendation that for patients at low (unlikely) VTE risk, using d-dimer as the initial test reduces the need for diagnostic imaging. Our systematic review informed the American Society of Hematology guideline recommendations about d-dimer, V/Q scan and CTPA for PE diagnosis, and d-dimer and ultrasound for DVT diagnosis.

Follow-up of guidelines and impact on the management of suspected deep vein thrombosis in emergency departments

AIMS

To evaluate the implementation of the European Society of Cardiology (ESC) guidelines concerning the diagnostic management of deep vein thrombosis (DVT) in emergency departments (ED); and to estimate the additional financial cost and the increase in the time spent in the ED if the guidelines are not followed.

PATIENTS AND METHODS

Retrospective, bi-centric study including all patients directly admitted or referred to the ED for a suspected isolated DVT, between April 1, 2019, and July 30, 2019. The diagnostic management was compared to the 2017 ESC's guidelines.

RESULTS

107 patients were included, 13 had DVT (12%) and three had superficial venous thrombosis (3%). A total of 26 patients (24%) had a diagnostic management according to guidelines. In 72 patients (67%), no assessment of clinical probability score was found. Among the 35 patients in whom a clinical probability score was calculated, 5 patients had an unnecessary D-dimer assay and 2 patients had unjustified imaging. The median time spent in the ED was 185minutes when the recommendations were followed, and 250minutes when they were not (P=0.317). The total estimated additional cost was €232.20.

CONCLUSION

The rate of adherence to the guidelines is low, mainly due to the absence of calculation of a clinical probability. This leads, in addition to the risk of diagnostic error, to an increase in the time spent in the EDs and inappropriate use of the technical platform, resulting in additional costs of care.

Appropriate use of D-dimer testing can minimize over-utilization of venous duplex ultrasound in a contemporary high-volume hospital

BACKGROUND

The sensitivity of d-dimer (DD) in detecting deep venous thrombosis (DVT) is remarkably high; however, many institutions send patients immediately for a venous duplex ultrasound (VDU). This study was designed to examine the appropriate utilization of DD and VDU in a high-volume hospital.

METHODS

A retrospective study was conducted on consecutive patients who presented to a high-volume emergency department (ED) with lower extremity limb swelling/pain over a 30-day period, who were sent for VDU during an evaluation for DVT. VDU data were merged with electronic DD laboratory results. The enzyme-linked immunosorbent assay method was used to provide DD values and thresholds. Values above 0.60 mg/fibrinogen equivalent unit (FEU) were considered abnormal.

RESULTS

We reviewed the medical records of 517 ED patients in the month of June 2013. After applying the Wells criteria, 157 patients (30.4%) were excluded because of a history of DVT or pulmonary embolism, having been screened for shortness of breath, or sent for surveillance-leaving 360 for analysis. The average age was 59.3 ± 16.5 years with more women (210, 58.3%) and the majority reported limb pain or swelling (73.9%). DD was performed on 51 patients with an average value of 3.6 ± 5.4 mg/FEU, of which 43 (84.3%) were positive. DD identified all positive and negative DVT patients (100% sensitivity and negative predictive value), but also included 40 false positives (16.7% specificity). On the other hand, 309 patients were sent directly to VDU without DD; of those, 43 (13.9%) were positive for DVT. However, 266 (86.1%) patients were negative for DVT by VDU without DD and these were deemed improper by our current study protocol. Potential charge savings were calculated as VDU for all (360 × $1000 = $360,000), DD for all (360 × $145 = $52,200), and VDU for both true and false positives (estimated to be about 25% of the cases; 90 × $1000 = $90,000); this equals a charge savings of $217,800 and would avoid unnecessary VDUs.

CONCLUSIONS

Based on the results of our study, we suggest that the DD test be utilized during the initial work-up for patients with limb swelling/pain in the emergency room. Appropriate utilization of DD, as well as other clinical criteria, may limit the over-utilization and added cost of VDU, without a negative impact on patient care. The results of DD tests should be utilized to limit the number of patients sent for VDU to only those patients with a positive DD or other significant underlying concerns.

The Wells rule and D-dimer for the diagnosis of isolated distal deep vein thrombosis

BACKGROUND

Pretest clinical probability with the Wells rule and D-dimer have been widely investigated for the diagnosis of symptomatic proximal deep vein thrombosis (DVT) of the lower limbs, but they have not been formally tested for symptomatic isolated distal DVT diagnosis.

OBJECTIVE

To evaluate the diagnostic accuracy of the Wells rule and D-dimer for isolated distal DVT.

DESIGN, SETTING, AND PATIENTS

This was a single-center, cross-sectional study including 873 consecutive outpatients with suspected DVT, in whom pretest clinical probability determination, D-dimer determination (STA Liatest; cut-off of < 500 ng mL(-1) ) and complete compression ultrasonography of both lower limbs were performed.

RESULTS

The isolated distal DVT prevalence was 12.4% (90/725). The sensitivity of the Wells rule for isolated distal DVT was 47% (95% confidence interval [CI] 36-57%), the specificity was 74% (95% CI 70-77%), and the negative and positive predictive values were 91% (95% CI 88-93%) and 20% (95% CI 15-26%), respectively. Patients with isolated distal DVT had higher D-dimer levels than patients without DVT (1759 ± 1576 vs. 862 ± 1079 ng mL(-1) , P = 0.0001). D-dimer was negative in 13 patients with isolated distal DVT. D-dimer sensitivity and specificity for isolated distal DVT were 84% (95% CI 75-91%) and 50% (95% CI 46-54%), respectively, with a negative predictive value of 96% (95% CI 93-98%). In patients with low pretest clinical probability, the D-dimer negative predictive value was 99% (95% CI 95-100%).

CONCLUSION

In clinically suspected DVT with negative proximal compression ultrasonography, pretest clinical probability with the Wells rule has a low diagnostic accuracy for isolated distal DVT. D-dimer has a better negative predictive value, but alone it does not exclude isolated distal DVT. In patients with low pretest clinical probability, D-dimer had a negative predictive value of > 95% for isolated distal DVT.

Non-compressibility ratio of sonography in deep venous thrombosis

BACKGROUND

The risk of post-thrombotic syndrome and pulmonary embolism can be increased if there is failure to diagnose deep venous thrombosis (DVT) promptly. Emergency physicians (EPs) need a quick and readily available test to diagnose, treat and help them decide whether to discharge or admit DVT patients in a timely manner. The aim of this study was to investigate the value of the non-compressibility ratio of thrombosed veins in DVT patients, and give EPs an objective value to aid them in their decision-making with regard to DVT patients in the emergency department.

METHODS

We reviewed 34 adult patients with DVT diagnosed by sonography in an emergency department. Medical records including demographic data and sonography results were retrospectively reviewed and analyzed.

RESULTS

Mean age was 72.9 ± 16.5 years. Group I comprised 14 patients (41.2%) who had DVT in the popliteal and femoral veins. Group II comprised 8 patients (23.5%) who had DVT isolated to the popliteal vein and 12 patients (35.3%) who had DVT isolated to the femoral vein. Group I had a significantly higher non-compressibility ratio than Group II (93.4 ± 6.2% vs. 80.1 ± 19.2%, p < 0.05). The area under the receiver operating characteristic curve of the non-compressibility ratio between discriminating groups was 0.711 (95% confidence interval, 0.527-0.854; p < 0.05). The clinical prognostic score of Group I was significantly higher than that of Group II (6.2 ± 1.8 vs. 4.1 ± 2.6, p < 0.05). There was a significant positive correlation between the non-compressibility ratio of the thrombosed vein and the clinical prognostic score (p = 0.001).

CONCLUSION

The non-compressibility ratio of the thrombosed vein provides EPs with an objective test to evaluate the severity of DVT and to admit patients for consideration of adverse outcomes.

Freqüência da profilaxia mecânica para trombose venosa profunda em pacientes internados em uma unidade de emergência de Maceió

CONTEXTO: A trombose venosa profunda (TVP) é uma doença de ocorrência multidisciplinar e freqüente, incluindo as complicações relacionadas a ela, como o tromboembolismo pulmonar (TEP). Sendo a profilaxia mecânica um dos melhores (por seu baixo custo e eficácia comprovada) e mais simples meios para reduzir sua incidência, é de grande relevância que se pesquise sua utilização visando benefícios para o paciente e o serviço hospitalar. OBJETIVO: Determinar a freqüência da utilização da profilaxia mecânica para TVP na Unidade de Emergência Dr. Armando Lages em Maceió (AL). MÉTODOS: Foi realizado um estudo transversal descritivo na unidade durante o período de 8 meses. A amostra foi calculada em 282 pacientes internados nas unidades de enfermarias das diversas especialidades. Os dados foram coletados em prontuários e mediante entrevista ao paciente. No prontuário de cada paciente foi pesquisada a utilização da profilaxia mecânica para TVP, além de diversos fatores para a estratificação do risco, segundo a Sociedade Brasileira de Angiologia e Cirurgia Vascular. O estudo estatístico foi realizado através do software SPSS, utilizando o teste qui-quadrado considerando o valor de p < 0,05. RESULTADOS: Foram analisados 282 pacientes, sendo 181 (64%) homens e 101 (36%) mulheres, com idade média de 54,1 anos. Quanto ao risco, 210 (74,5%) foram classificados como alto risco, 56 (19,8%) como moderado risco e 16 (5,7%) como baixo risco. Do total de pacientes, 234 (83%) não receberam profilaxia e 48 (17%) receberam. Não houve diferença estatística entre os dados obtidos na pesquisa e os encontrados na literatura (p = 0,065). CONCLUSÕES: Apesar de ter sua eficácia comprovada e difundida, a profilaxia mecânica para TVP ainda não atinge níveis satisfatórios de utilização.

Venothromboembolism

This article focuses on the clinical presentation, diagnosis, and management of veno-thromboembolism, including deep venous thrombosis (DVT) and pulmonary embolism (PE), from the perspective of the emergency physician. The discussion is divided into two sections: DVT and PE. Because veno-thromboembolism is a continuum, certain aspects, such as background, incidence, the use of D dimer, and anticoagulation of both DVT and PE, are discussed together. Heavier emphasis is placed on topics germane to the emergency physician, and considerations for special populations are reviewed.

Uses of different D-dimer levels can reduce the need for venous duplex scanning to rule out deep vein thrombosis in patients with symptomatic pulmonary embolism

OBJECTIVE

This study investigated the prevalence and distribution of deep vein thrombosis (DVT) in patients with symptomatic pulmonary embolism (PE) to establish a screening protocol to reduce unnecessary venous duplex scanning using different D-dimer level rather than single cutoff point of 0.5 microg/mL in patients with low and moderate pretest clinical probability (PTP).

METHODS

The PTP score and D-dimer testing were used to evaluate 85 consecutive patients with symptomatically proven PE before venous duplex scanning. After calculating the PTP score, patients were divided into low (<or=0 points), moderate (1 to 2 points), and high (>or=3 points) PTP groups. The receiver operating characteristic (ROC) curves analysis was used to determine the appropriate D-dimer cutoff point in low and moderate PTP, with a negative predictive value of >98%.

RESULTS

The study enrolled 81 patients. The prevalence of DVT was 63%, with 27 patients (33%) classified as low, 38 (47%) as moderate, and 16 (20%) as high PTP. DVT was detected in nine patients (33%) in the low PTP group, in 27 (71%) in the moderate group, and in 15 (94%) in the high group. In the low PTP patients, the difference in the value of D-dimer assay between positive-scan and negative-scan patients was statistically significant (9.99 +/- 7.33 vs 3.46 +/- 4.20, respectively; P = .008). Conversely, no significant difference in the D-dimer assay value between positive and negative scan results was found in the moderate PTP patients. ROC curves analysis were used to select D-dimer cutoff points of 2.0 microg/mL for the low PTP group and 0.7 microg/mL for the moderate PTP groups. For both groups, D-dimer testing provided 100% sensitivity and 100% negative predictive value in the diagnosis of DVT. In the low PTP group, specificity increased from 33% to 67% (P = .046). In the moderate PTP group, however, the determined D-dimer level did not improve the specificity. Overall, venous duplex scanning could have been reduced by 17% (14/81) by using different D-dimer cutoff points.

CONCLUSIONS

A combination of specific D-dimer level and clinical probability score is most effective in the low PTP patients in excluding DVT. In the moderate PTP group, however, the recommended cutoff point of 0.5 microg/mL may be preferable. These results show that a different D-dimer level is more useful than single cutoff point of 0.5 microg/mL in excluding DVT in established PE patients.

AT, Sobreira MDL, Santos FC, Giannini M, Maffei FHDA. Avaliação do modelo de predição clínica de Wells et al. no diagnóstico da trombose venosa profunda dos membros inferiores

CONTEXTO: A aplicação de uma estratégia baseada em um modelo clínico associado ao mapeamento dúplex (MD) pode permitir um diagnóstico da trombose venosa profunda (TVP) mais seguro, eficaz e custo-efetivo. OBJETIVO: Testar o modelo clínico de Wells et al. associado ao MD e verificar a ocorrência de TVP nos pacientes categorizados quanto à probabilidade de apresentar a doença, e determinar se, a partir dos resultados obtidos, seria possível reduzir o número de exames seriados com o MD. MÉTODOS: Os pacientes com suspeita clínica de TVP foram categorizados quanto à apresentação de TVP em baixa, moderada e alta probabilidade (BP, MP, AP) e, em seguida, submetidos ao MD. Pacientes com MD negativo repetiram o exame em 24-48 horas e em 7 dias. Pacientes com exame positivo para TVP foram tratados. Todos os pacientes sem TVP foram convocados para reavaliação clínica em 3 meses. RESULTADOS: A ocorrência de TVP entre os 489 pacientes avaliados foi de 39,1% (191), sendo 35,6% identificados no exame inicial e 3,5% no exame seriado. Os índices de pacientes que apresentaram TVP foram de 6,1% no grupo de BP, 26,9% no grupo de MP e 79,5% no grupo de AP. No exame seriado, o percentual de TVP foi de 2,4, 7,8 e 15,1% nos grupos BP, MP e AP, respectivamente. Dos pacientes com MD negativo, 62,4% compareceram após 3 meses, e piora dos sintomas foi apresentada por apenas um paciente. Neste, o MD mostrou TVP de veia poplítea. CONCLUSÃO: Os resultados obtidos sugerem que, para os pacientes com BP para TVP e MD negativo, seria possível prescindir do exame seriado, devido à baixa ocorrência de TVP neste grupo, tornando, assim, a abordagem diagnóstica mais simples.

Review of the evidence on diagnosis of deep venous thrombosis and pulmonary embolism

PURPOSE

This review summarizes the evidence regarding the efficacy of techniques for diagnosis of deep venous thrombosis (DVT) and pulmonary embolism.

METHODS

We searched for studies using MEDLINE, MICROMEDEX, the Cochrane Controlled Trials Register, and the Cochrane Database of Systematic Reviews through June 2006. We reviewed randomized controlled trials, systematic reviews of trials, and observational studies if no trials were available. Paired reviewers assessed the quality of each included article and abstracted the data into summary tables. Heterogeneity in study designs precluded mathematical combination of the results of the primary literature.

RESULTS

Our review found 22 relevant systematic reviews and 36 primary studies. The evidence strongly supports the use of clinical prediction rules, particularly the Wells model, for establishing the pretest probability of DVT or pulmonary embolism in a patient before ordering more definitive testing. Fifteen studies support that when a D-dimer assay is negative and a clinical prediction rule suggests a low probability of DVT or pulmonary embolism, the negative predictive value is high enough to justify foregoing imaging studies in many patients. The evidence in 5 systematic reviews regarding the use of D-dimer, in isolation, is strong and demonstrates sensitivities of the enzyme-linked immunosorbent assay (ELISA) and quantitative rapid ELISA, pooled across studies, of approximately 95%. Eight systematic reviews found that the sensitivity and specificity of ultrasonography for diagnosis of DVT vary by vein; ultrasonography performs best for diagnosis of symptomatic, proximal vein thrombosis, with pooled sensitivities of 89% to 96%. The sensitivity of single-detector helical computed tomography for diagnosis of pulmonary embolism varied widely across studies and was below 90% in 4 of 9 studies; more studies are needed to determine the sensitivity of multidetector scanners.

CONCLUSIONS

While the strength of the evidence varies across questions, it is generally strong.

Current diagnosis of venous thromboembolism in primary care: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians

This guideline summarizes the current approaches for the diagnosis of venous thromboembolism. The importance of early diagnosis to prevent mortality and morbidity associated with venous thromboembolism cannot be overstressed. This field is highly dynamic, however, and new evidence is emerging periodically that may change the recommendations. The purpose of this guideline is to present recommendations based on current evidence to clinicians to aid in the diagnosis of lower extremity deep venous thrombosis and pulmonary embolism.

Profilaxia para tromboembolismo venoso em um hospital de ensino

OBJETIVO: Verificar se a profilaxia da trombose venosa profunda está sendo utilizada de maneira correta e rotineira em um hospital de ensino. MÉTODOS E CASUÍSTICA: Foi realizado um estudo transversal de pacientes internados em sete setores (enfermarias) do Conjunto Hospitalar de Sorocaba (Hospital de Ensino), no período de agosto de 2004 a agosto de 2005. Para estratificação do risco de trombose venosa profunda de cada paciente, foram pesquisados fatores clínicos e cirúrgicos, segundo o protocolo preconizado pela Sociedade Brasileira de Angiologia e Cirurgia Vascular. No período estudado, foram analisados 216 prontuários, dos quais 30 eram da cirurgia abdominal, 30 da cirurgia vascular, 30 da urologia, 31 da clínica médica, 31 da unidade de terapia intensiva, 31 da ortopedia e 33 da ginecologia/obstetrícia. RESULTADOS: Do total de pacientes, foi efetuada profilaxia para trombose venosa profunda em 57 (26%), sendo que, em 51 (89%), a execução foi de maneira correta e, em 6 (11%), não-preconizada. O método profilático mais utilizado foi o medicamentoso; 49 de 57 pacientes fizeram uso de heparina de baixo peso molecular. Também foi verificada a utilização de meias elásticas em cinco pacientes e deambulação precoce em sete. Já a compressão pneumática intermitente não foi utilizada em nenhum deles. CONCLUSÃO: De acordo com os resultados e com base no protocolo, concluiu-se que, no período da pesquisa, a profilaxia para trombose venosa profunda, no Conjunto Hospitalar de Sorocaba, foi executada rotineiramente e de forma adequada em apenas 23,6% (51 do total de 216 pacientes).

D-dimer testing: advantages and limitations in emergency medicine for managing acute venous thromboembolism

D-dimer values can be rapidly determined and used for the management of acute venous thromboembolism (VTE). However, its role in the setting of emergency still remains unclear and inappropriate testing is a significant clinical problem. This review discusses the currently used assays, clinical indications, and limitations of D-dimer measurement. Studies in English language were identified by searching PubMed from December 1985 to December 2005. Available literature on D-dimer was identified from Medline, along with cross referencing from the reference lists of major articles and reviews on this subject. Among 56 articles collected, 14 papers, 4 overviews and 1 systemic review were selected accordingly to predefined criteria. Data synthesis shows that D-dimer testing has sufficient diagnostic accuracy for ruling out acute VTE if used in combination with standardised clinical judgement. D-dimer seems to be also a useful tool for managing suspected VTE patients in absence of immediate imaging. Attention should be paid to exclude conditions that may affect the accuracy of the test, such as concomitant disease, heparin administration and symptom duration >15 days. Although enzyme-linked immunosorbent assay determination has the highest accuracy, immunoturbidimetric assay seems the most suitable on an emergency basis because of its rapid performance. In conclusion, at present D-dimer testing can be safely used in the management of acute VTE in emergency medicine. However, because of its heterogeneity related to the method used and setting implemented, it is preferable to assess D-dimer accuracy before its implementation in management strategies for VTE.

Prospective Evaluation of a Screening Protocol to Exclude Deep Vein Thrombosis on the Basis of a Combination of Quantitative D-Dimer Testing and Pretest Clinical Probability Score

BACKGROUND

Clinical signs and symptoms such as swelling, pain, and redness are unreliable markers of deep vein thrombosis (DVT). Because of this venous duplex scanning (VDS) has been heavily used in DVT detection. The purpose of this study was to determine if a combination of D-dimer testing and pretest clinical score could reduce the use of VDS in symptomatic patients with suspected DVT.

STUDY DESIGN

One hundred seventy-four consecutive patients with suspected DVT were prospectively evaluated using pretest clinical probability (PCP) score and D-dimer testing before VDS. After calculating clinical probability scores developed by Wells and associates, patients were divided into low risk (<or= 0 points), moderate risk (1 to 2 points), and high risk (>or=3 points) PCP.

RESULTS

One hundred fifty-eight patients were enrolled. The prevalence of DVT in this study was 37%. Thirty-eight patients (24%) were classified as low risk, 64 (41%) as moderate risk, and 56 (35%) as high risk PCP. DVT was identified in only one patient (2.6%) with low risk PCP. In contrast, DVT was found in 22 (34%) with moderate risk, and 35 (63%) with high risk PCP. In the high and moderate risk PCP groups, positive scan patients had a markedly higher value of D-dimer assay than negative scan patients (p=0.0001 and p=0.0057, respectively). In the low risk PCP patients, D-dimer testing provided 100% sensitivity, 46% specificity, 4.8% positive predictive value, and 100% negative predictive value in the diagnosis of DVT. Similarly, in the moderate risk PCP, the D-dimer testing showed 100% sensitivity, 45% specificity, 49% positive predictive value, and 100% negative predictive value. In the high risk group, D-dimer testing achieved 100% sensitivity, 57% specificity, 80% positive predictive value, and 100% negative predictive value in the diagnosis of DVT. These results suggested that 36 of 158 patients who had a non-high PCP (low and moderate PCP) and a normal D-dimer concentration were considered to have no additional investigation, so VDS could have been reduced by 23% (36/158).

CONCLUSIONS

A combination of D-dimer testing and clinical probability score may be effective in avoiding unnecessary VDS in suspected symptomatic DVT in the low and moderate PCP patients. The need for VDS could be reduced by 23% despite a relatively high prevalence of DVT.

Variation in the diagnostic performance of D-dimer for suspected deep vein thrombosis

BACKGROUND

Numerous studies have evaluated the accuracy of D-dimer in diagnosing suspected deep vein thrombosis (DVT), but results are conflicting.

AIM

To overview estimates of the diagnostic accuracy of D-dimer and identify causes of variation.

DESIGN

Systematic review, meta-analysis and meta-regression.

METHODS

We searched Medline, EMBASE, CINAHL, Web of Science, Cochrane Database of Systematic Reviews, Cochrane Controlled Trials Register, Database of Reviews of Effectiveness, the ACP Journal Club, citation lists, and contacted manufacturers. We selected studies that compared D-dimer to a reference standard in patients with suspected DVT. Data were analysed by random effects meta-analysis and meta-regression.

RESULTS

We included 97 studies reporting 198 assays in 99 different patient groups. Overall estimated sensitivity and specificity of D-dimer were 90.5% and 54.7%, but both estimates were subject to significant heterogeneity (p < 0.001). Meta-regression identified that some heterogeneity was explained by study setting, exclusion criteria, whether recruitment was consecutive or the study prospective, whether D-dimer and the reference standard were measured blind, and whether the D-dimer threshold was determined a priori. Sensitivity and specificity also varied between ELISA (94% and 45% respectively), latex (89% and 55%) and whole blood agglutination assays (87% and 68%). Sensitivity was higher for proximal than distal DVT. Specificity was dependent upon whether clinical probability of DVT was high (specificity 51%), intermediate (67%) or low (78%).

DISCUSSION

D-dimer has good sensitivity, but poor specificity, for DVT. Estimates are subject to substantial heterogeneity from various sources. D-dimer specificity appears to be strongly dependent upon the pre-test clinical probability of DVT.

Deep vein thrombosis

Deep vein thrombosis and its sequelae pulmonary embolism and post-thrombotic syndrome are some of the most common disorders. A thrombus either arises spontaneously or is caused by clinical conditions including surgery, trauma, or prolonged bed rest. In these instances, prophylaxis with low-dose anticoagulation is effective. Diagnosis of deep vein thrombosis relies on imaging techniques such as ultrasonography or venography. Only about 25% of symptomatic patients have a thrombus. Thus, clinical risk assessment and D-dimer measurement are used to rule out deep vein thrombosis. Thrombus progression and embolisation can be prevented by low-molecular-weight heparin followed by vitamin K antagonists. Use of these antagonists for 3-6 months is sufficient for many patients. Those with antithrombin deficiency, the lupus anticoagulant, homozygous or combined defects, or with previous deep vein thrombosis can benefit from indefinite anticoagulation. In cancer patients, low-molecular-weight heparin is more effective than and is at least as safe as vitamin K antagonists. Women seem to have a lower thrombosis risk than men, but pregnancy or use of oral contraceptives or hormone replacement therapy represent important risk factors.

Preliminary validation of clinical assessment for deep vein thrombosis in orthopaedic outpatients

The purpose of our study was to determine if a previously published clinical decision rule designed to estimate the probability of proximal deep vein thrombosis in outpatients is valid when applied exclusively to outpatients with musculoskeletal disorders. We also sought to determine whether probability estimates differed for patients with or without trauma, fracture, or recent orthopaedic surgery. Data collected from outpatients with surgical and nonsurgical musculoskeletal disorders (n = 464) were extracted from the datasets of three previously published studies done on heterogeneous groups of patients (n = 3424). Followup for all patients was 3 months. Testing of all patients for thromboembolic disease was done using validated diagnostic procedures. Probability estimates for orthopaedic outpatients were consistent with estimates from published studies. The proportion of patients who had venous thromboembolism was 5.6% (95% confidence interval, 3.5-8.7%) for the low probability group, 14.1% (95% confidence interval, 8.6-22.4%) for the moderate probability group, and 47.4% (95% confidence interval, 35.3-60%) for the high probability group. Validity estimates for patients with and without recent trauma, surgery, or fracture differed, but not dramatically. The validity of the clinical decision rule as applied to outpatients with musculoskeletal disorders was supported.

Usefulness of clinical prediction rules for the diagnosis of venous thromboembolism: a systematic review

PURPOSE

To summarize the evidence on the predictive value of clinical prediction rules for the diagnosis of venous thromboembolism.

METHODS

We selected all studies in the English literature in which a clinical prediction rule was prospectively validated against a reference standard, and calculated likelihood ratios, predictive values, and the area under the receiver operating characteristic (ROC) curve for each prediction rule.

RESULTS

Twenty-three studies met our eligibility criteria: 17 evaluated prediction rules for the diagnosis of deep venous thrombosis and six evaluated rules for pulmonary embolism. The most frequently evaluated prediction rule for deep vein thrombosis was the Wells rule, which had median positive likelihood ratios of 6.62 for patients with a high pretest probability, 1 for moderate pretest probability, and 0.22 for low pretest probability. The median area under the ROC curve was 0.82. Addition of the D-dimer test to the prediction rule increased the median area under the curve to 0.90. The Wells prediction rule was the most commonly studied for pulmonary embolus and had median positive likelihood ratios of 6.75 for those with high pretest probability, 1.82 for moderate pretest probability, and 0.13 for low pretest probability. The median area under the ROC curve was 0.82.

CONCLUSION

The Wells prediction rule is useful in identifying patients at low risk of being diagnosed with venous thromboembolism. The addition of a rapid latex D-dimer assay improved the overall performance of the prediction rule.

Combined use of rapid D-dimer testing and estimation of clinical probability in the diagnosis of deep vein thrombosis: systematic review

OBJECTIVE

To summarise the evidence supporting the use of rapid d-dimer testing combined with estimation of clinical probability to exclude the diagnosis of deep venous thrombosis among outpatients.

DATA SOURCES

Medline (June 1993 to December 2003), the Database of Abstracts and Reviews (DARE), and reference lists of studies in English.

SELECTION OF STUDIES

We selected 12 studies from among 84 reviewed. The selected studies included more than 5000 patients and used a rapid D-dimer assay and explicit criteria to classify cases as having low, intermediate, or high clinical probability of deep vein thrombosis of the lower extremity among consecutive outpatients.

REVIEW METHODS

Diagnosis required objective confirmation, and untreated patients had to have at least three months of follow up. The outcome was objectively documented venous thromboembolism. Two authors independently abstracted data by using a data collection form.

RESULTS

When the less sensitive SimpliRED D-dimer assay was used the three month incidence of venous thromboembolism was 0.5% (95% confidence interval 0.07% to 1.1%) among patients with a low clinical probability of deep vein thrombosis and normal D-dimer concentrations. When a highly sensitive D-dimer assay was used, the three month incidence of venous thromboembolism was 0.4% (0.04% to 1.1%) among outpatients with low or moderate clinical probability of deep vein thrombosis and a normal D-dimer concentration.

CONCLUSIONS

The combination of low clinical probability for deep vein thrombosis and a normal result from the SimpliRED D-dimer test safely excludes a diagnosis of acute venous thrombosis A normal result from a highly sensitive D-dimer test effectively rules out deep vein thrombosis among patients classified as having either low or moderate clinical probability of deep vein thrombosis.

The utility of pretest probability assessment in patients with clinically suspected venous thromboembolism

The assessment of pretest probability (PTP), with stratification into low-, intermediate- and high-risk groups is an essential initial step in the current diagnostic management of patients with suspected venous thromboembolism (VTE). In combination with additional information, it reduces the need for initial and supplementary imaging, and allows considerable refinement of the posterior probability of VTE following non-invasive imaging. PTP may be assessed either empirically or by using various decision rules or scoring systems, the best known of which are the simplified Wells scores for suspected deep vein thrombosis (DVT) and pulmonary embolism (PE), and the Geneva score for suspected PE. Each of these approaches shows similar directional and categorical accuracy, and has been validated as facilitating clinically useful classification of the PTP, although an overview of data suggests that fewer patients tend to be classified as low PTP when assessed empirically. This group is the most important to identify, as several outcome studies have shown that imaging and treatment are safely obviated in outpatients with suspected DVT or PE who have a low PTP in combination with negative d-dimer testing, a subgroup accounting for up to half of all patients studied. Hence, while probably not of critical importance, the explicit approach offered by scoring systems might be preferred over empirical assessment, particularly when used by more junior staff.

Role of fibrin D-dimer testing in emergency medicine

OBJECTIVES

Systemic values of the fibrinolytic plasma marker fibrin D-dimer are raised in a variety of acute clinical conditions. D-dimer values can now be rapidly determined and used to aid diagnosis in emergency medicine. However, despite clinical guidelines, inappropriate and unnecessary measurement of D-dimer values is a significant clinical problem. An understanding of the pathophysiological basis and limitations of the value of D-dimer values may help reduce this problem. This review discusses the pathophysiology of the fibrinolytic system. The currently used assays, clinical indications, and limitations of D-dimer measurement are reviewed. Finally, the potential future clinical indications for measurement of D-dimer values in emergency medicine are discussed.

METHODS

Literature on D-dimer was identified from Medline, along with cross referencing from the reference lists of major articles on the subject

RESULTS

and conclusions: Systemic D-dimer values aids diagnosis, and is potentially a prognostic indicator, in a variety of clinical conditions in emergency medicine. However, it has limited specificity in patients with comorbid conditions. Although, currently, there is no standard D-dimer assay, immunoturbidimetric assays are the most suitable for use in emergency medicine