Management of patients with suspected deep vein thrombosis in the emergency department: combining use of a clinical diagnosis model with D-dimer testing

Serum D-dimer should not be used in the diagnosis of venous thromboembolism within 28 days of total knee replacement surgery

Background

Serum D-dimer is frequently used to rule out a diagnosis of venous thromboembolism (VTE), a recognised complication following total knee replacement (TKR). TKR is known to cause a rise in D-dimer levels, reducing its specificity. Previous studies have demonstrated that D-dimer remains elevated within 10 days of TKR and therefore should be avoided. The aim of this study was to determine whether serum D-dimer tests are clinically appropriate in identifying VTE when performed within 28 days of TKR.

Methods

Case notes for patients who had a serum D-dimer test performed for clinically suspected VTE at ≥ 28 days following TKR were retrospectively reviewed for a 6-year period. Demographics, D-dimer result, time after surgery and further radiological investigations were recorded.

Results

Fifty patients underwent D-dimer tests at ≥ 28 days following surgery (median 60 days, range 29–266); 48 of these patients had a positive result. Of these, five had confirmed VTE on radiological investigations. Serum D-dimer was raised in 96% of the patients. Only 10.42% of these patients had confirmed VTE. No patients with negative D-dimers had confirmed VTE.

Conclusions

These findings suggest that serum D-dimer remains raised for at least 28 days and possibly considerably longer following TKR. Serum D-dimer should not be used in patients with clinically suspected VTE within this period because of its unacceptably low specificity of 4.44% and positive predictive value of 10.42%, which can lead to a delay in necessary further radiological investigations, waste of resources and unnecessary exposure to harm.

Diagnosing deep vein thrombosis in cancer patients with suspected symptoms: An individual participant data meta-analysis

BACKGROUND

A previous individual participant data (IPD) meta-analysis showed that the Wells rule and D-dimer testing cannot exclude suspected deep vein thrombosis (DVT) in cancer patients.

OBJECTIVES

To explore reasons for this reduced diagnostic accuracy and to optimize the diagnostic pathway for cancer patients suspected of DVT.

PATIENTS AND METHODS

Using IPD from 13 studies in patients with suspected DVT, DVT prevalence and the predictive value of the Wells rule items and D-dimer testing were compared between patients with and without cancer. Next, we developed a prediction model with five variables selected from all available diagnostic predictors.

RESULTS

Among the 10 002 suspected DVT patients, there were 834 patients with cancer. The median prevalence of DVT in these patients with cancer was 37.5% (interquartile range [IQR], 30.8-45.5), whereas it was 15.1% (IQR, 11.5-16.7) in patients without cancer. Diagnostic performance of individual Wells rule items and D-dimer testing was similar across patients with and without cancer, except "immobility" and "history of DVT." The newly developed rule showed a pooled c-statistic 0.80 (95% confidence interval [CI], 0.75-0.83) and good calibration. However, using this model, still only 4.3% (95% CI, 3.0-5.7) of the suspected patients with cancer could be identified with a predicted DVT posttest probability of <2%.

CONCLUSIONS

Likely because of the high prevalence of DVT, clinical models followed by D-dimer testing fail to rule out DVT efficiently in cancer patients suspected of DVT. Direct referral for compression ultrasonography appears to be the preferred approach for diagnosis of suspected DVT in cancer patients.

Validation of STA-Liatest D-Di assay for exclusion of pulmonary embolism according to the latest Clinical and Laboratory Standard Institute/Food and Drug Administration guideline. Results of a multicenter management study

Combined clinical pretest probability (PTP) and D-dimer testing have great diagnostic value for pulmonary embolism exclusion. To harmonize performance levels of D-dimer assays available on the market, the Clinical and Laboratory Standard Institute (CLSI) has published a guideline, endorsed by the US Food and Drug Administration (FDA). Such guideline specifies the ideal D-dimer assay characteristic and target population. This study was conducted following the CLSI guideline to upgrade the assay-intended use and obtain FDA clearance of STA-Liatest D-Di assay for pulmonary embolism exclusion in patient with low/moderate PTP. This was an international, multicenter, prospective nonrandomized, noninterventional clinical outcome management study conducted in a standard of care setting. D-dimer assay was performed in consecutive, ambulatory outpatients suspected of pulmonary embolism, with low/moderate PTP, and without medical conditions or in clinical settings known to alter default D-dimer values regardless of the presence of thrombosis using a threshold of 0.5 μg/ml (fibrinogen equivalent units) for venous thromboembolism exclusion. Results were used to determine test performance. Of 1141 patients who underwent D-dimer testing, 1060 had valid results and completed study as planned. STA-Liatest D-Di assay performance has exceeded the CLSI/FDA guidance requirements, with a sensitivity of 97.6% (95% confidence interval: 91.7–99.7%) and a negative predictive value of 99.7% (95% confidence interval: 99.0–100%). STA-Liatest D-Di assay has an excellent performance when used in combination with a PTP score in relevant patients and has the potential to minimize the economic healthcare burden avoiding unnecessary and expensive imaging tests.

A systematic review of clinical prediction scores for deep vein thrombosis

Objective Diagnosis of deep vein thrombosis remains a challenging problem. Various clinical prediction rules have been developed in order to improve diagnosis and decision making in relation to deep vein thrombosis. The purpose of this review is to summarise the available clinical scores and describe their applicability and limitations. Methods A systematic search of PubMed, MEDLINE and EMBASE databases was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidance using the keywords: clinical score, clinical prediction rule, risk assessment, clinical probability, pretest probability, diagnostic score and medical Subject Heading terms: 'Venous Thromboembolism/diagnosis' OR 'Venous Thrombosis/diagnosis'. Both development and validation studies were eligible for inclusion. Results The search strategy returned a total of 2036 articles, of which 102 articles met a priori criteria for inclusion. Eight different diagnostic scores were identified. The development of these scores differs in respect of the population included (hospital inpatients, hospital outpatients or primary care patients), the exclusion criteria, the inclusion of distal deep vein thrombosis and the use of D-dimer. The reliability and applicability of the scores in the context of specific subgroups (inpatients, cancer patients, elderly patients and those with recurrent deep vein thrombosis) remains controversial. Conclusion Detailed knowledge of the development of the various clinical prediction scores for deep vein thrombosis is essential in understanding the power, generalisability and limitations of these clinical tools.

Exclusion of deep vein thrombosis using the Wells rule in clinically important subgroups: individual patient data meta-analysis

OBJECTIVE

To assess the accuracy of the Wells rule for excluding deep vein thrombosis and whether this accuracy applies to different subgroups of patients.

DESIGN

Meta-analysis of individual patient data.

DATA SOURCES

Authors of 13 studies (n = 10,002) provided their datasets, and these individual patient data were merged into one dataset.

ELIGIBILITY CRITERIA

Studies were eligible if they enrolled consecutive outpatients with suspected deep vein thrombosis, scored all variables of the Wells rule, and performed an appropriate reference standard.

MAIN OUTCOME MEASURES

Multilevel logistic regression models, including an interaction term for each subgroup, were used to estimate differences in predicted probabilities of deep vein thrombosis by the Wells rule. In addition, D-dimer testing was added to assess differences in the ability to exclude deep vein thrombosis using an unlikely score on the Wells rule combined with a negative D-dimer test result.

RESULTS

Overall, increasing scores on the Wells rule were associated with an increasing probability of having deep vein thrombosis. Estimated probabilities were almost twofold higher in patients with cancer, in patients with suspected recurrent events, and (to a lesser extent) in males. An unlikely score on the Wells rule (≤ 1) combined with a negative D-dimer test result was associated with an extremely low probability of deep vein thrombosis (1.2%, 95% confidence interval 0.7% to 1.8%). This combination occurred in 29% (95% confidence interval 20% to 40%) of patients. These findings were consistent in subgroups defined by type of D-dimer assay (quantitative or qualitative), sex, and care setting (primary or hospital care). For patients with cancer, the combination of an unlikely score on the Wells rule and a negative D-dimer test result occurred in only 9% of patients and was associated with a 2.2% probability of deep vein thrombosis being present. In patients with suspected recurrent events, only the modified Wells rule (adding one point for the previous event) is safe.

CONCLUSION

Combined with a negative D-dimer test result (both quantitative and qualitative), deep vein thrombosis can be excluded in patients with an unlikely score on the Wells rule. This finding is true for both sexes, as well as for patients presenting in primary and hospital care. In patients with cancer, the combination is neither safe nor efficient. For patients with suspected recurrent disease, one extra point should be added to the rule to enable a safe exclusion.

Value of D-dimer and protein S for diagnosis of portal vein thrombosis in patients with liver cirrhosis

OBJECTIVE

To investigate the value of D-dimer and protein S plasma concentrations for diagnosis of portal vein thrombosis (PVT) in patients with liver cirrhosis.

METHODS

D-dimer and protein S were quantified, PVT was diagnosed by dynamic enhanced computed tomography and liver function was classified using the Child-Pugh system. Receiver operating curve analysis was performed.

RESULTS

D-dimer increased, and protein S decreased, with decreasing liver function in the total study population (n = 188). D-dimer concentrations were significantly higher and protein S concentrations were significantly lower in patients with (n = 51) than those without PVT (n = 137). D-dimer had high specificity and negative predictive value (NPV) in Child-Pugh class A or B patients (cut-off values>0.56 mg/l and >1.18 mg/l, respectively). In class C patients>0.77 mg/l D-dimer had high sensitivity and NPV. Protein S had high sensitivity but low specificity in class A or B patients (cut-off values < 17.4 mg/l and <19.2 mg/l, respectively).

CONCLUSION

Plasma D-dimer and protein S are potential biomarkers for PVT diagnosis in patients with cirrhosis. PVT can be excluded when D-dimer is low and protein S is elevated.

Diagnostic approach to deep venous thrombosis and pulmonary embolism in the critical care setting

Considerable progress has been made during the last 30 years in the prevention, diagnosis, and therapy of venous thromboembolism. This article discusses the epidemiology, pathophysiology, and clinical presentation of the disease as well as the diagnostic uncertainty that exists in the critical care setting. Diagnostic approaches for deep venous thrombosis and pulmonary embolism are considered, including clinical prediction rules, D-dimer, contrast venography, duplex ultrasonography, computed tomographic angiography and venography, magnetic resonance imaging, ventilation–perfusion scanning, chest radiograph, arterial blood gases, electrocardiography, and echocardiography.

[Clinical usefulness of three quantitative D-dimers tests in outpatients with suspected deep vein thrombosis]

BACKGROUND AND OBJECTIVE

The diagnostic approach in outpatients with suspected deep vein thrombosis (DVT) of the lower limbs includes D-dimer measurement (DD). Elevated DD is not a diagnostic value for DVT. However, a normal value contributes to ruling out DVT. We do not know the best method to determine DD. Therefore, we have analyzed the clinical utility of three quantitative assays to determine DD in outpatients with suspected DVT.

PATIENTS AND METHODS

Consecutive outpatients with suspected DVT of the lower limbs who were referred to the DVT medical consultation were enrolled in the study. We used a diagnostic algorithm that included determining the pretest clinical probability (PCP) (Wells scale), DD level using three different quantitative methods (ELISA mini-VIDAS(®), Acure-care DDMR and DD-Plus). The DVT diagnosis was confirmed by seriated compression ultrasonography of the lower limbs. We analyzed the concordance between the three analytic methods to quantify DD and the characteristics.

RESULTS

A total of 306 patients (mean age 60 years, 62% women) with suspected DVT of the lower limbs were included. The compression ultrasonography confirmed the diagnosis of DVT in 23.8% of the patients. Anticoagulation treatment was not performed in patients in whom DVT was ruled out, and no thromboembolic event occurred during the 3 months of follow-up. The best concordance test results were between ELISA mini-VIDAS(®) and Acure-care DDMR assays. Both assays demonstrated elevated sensibility and a negative predictive value. ELISA mini-VIDAS(®) was the best analytic method for the subgroup of patients with low clinical probability.

CONCLUSIONS

The ELISA mini-VIDAS(®) method to determine DD rules out DVT in patients with low clinical probability.

Relationship between disease severity and D-dimer levels measured with two different methods in pulmonary embolism patients

Pulmonary embolism (PE) is diagnosed with increasing frequency nowadays due to advances in the diagnostic methods and the increased awareness of the disease. There is a tendency to use non invasive diagnostic methods for all diseases. D-dimer is a fibrin degradation product. We aimed to detect the relationship between disease severity and the D-dimer levels measured with two different methods. We compared D-dimer levels in cases of massive vs. non-massive PE. A total of 89 patients who were diagnosed between 2006 and 2008 were included in the study. Group 1 included patients whose D-dimer levels were measured with the immunoturbidimetric polyclonal antibody method (D-dimerPLUS^®), while Group 2 patients made use of the immunoturbidimetric monoclonal antibody method (InnovanceD-DIMER^®). In each group, the D-dimer levels of those with massive and non-massive PE were compared, using the Mann Whitney U test. The mean age of Group 1 (25 F/26 M) was 56.0 ± 17.9 years, and that of Group 2 (22 F/16 M) was 52.9 ± 17.9 years. There was no statistical difference in gender and mean age between the two groups (p > 0.05). In Group 1, the mean D-dimer level of massive cases (n = 7) was 1444.9 ± 657.9 μg/L and that of nonmassive PE (n = 34) was 1304.7 ± 350.5 μg/L (p > 0.05). In Group 2, the mean D-dimer level of massive cases (n = 6) was 9.7 ± 2.2 mg/L and that of non-massive PE (n = 32) was 5.9 ± 1.3 mg/L (p < 0.05). The mean D-dimer levels of massive cases as measured with the immunoturbidimetric monoclonal antibody method were significantly higher. Pulmonary embolism patients whose D-dimer levels are higher (especially higher than 6.6 mg/L) should be considered as possibly having massive embolism. Diagnostic procedures and management can be planned according to this finding.

Combined use of pretest clinical probability score and latex agglutination D-dimer testing for excluding acute deep vein thrombosis

OBJECTIVE

Currently, the latex agglutination D-dimer assay is widely used for excluding deep vein thrombosis (DVT) but is considered less sensitive than the enzyme-linked immunosorbent assay-based D-dimer test. The purpose of the present study was to determine if a combination of different cutoff points, rather than a single cutoff point of 1.0 microg/mL, on the latex agglutination D-dimer assay and the pretest clinical probability (PTP) score would be able to reduce the use of venous duplex ultrasound (DU) scanning in patients with suspected DVT.

METHODS

The PTP score and D-dimer testing were used to evaluate 989 consecutive patients with suspected DVT before venous DU scanning. After calculating the clinical probability scores, patients were divided into low-risk (< or =0 points), moderate-risk (1-2 points), and high-risk (> or =3 points) pretest clinical probability groups. Receiver operating characteristic (ROC) curve analysis was used to determine the appropriate D-dimer cutoff point for each PTP with a negative predictive value of >98% for a positive DU scan.

RESULTS

There were 886 patients enrolled. The study group included 609 inpatients (68.7%) and 277 outpatients (31.3%). The prevalence of DVT in this series was 28.9%. There were 508 patients (57.3%) classified as low-risk, 237 (26.8%) as moderate-risk, and 141 (14.9%) as high-risk PTP. DVT was identified in 29 patients (5.7%) with low-risk, 118 (49.8%) with moderate-risk, and 109 (77.3%) with high-risk PTP scores. ROC curve analysis was used to select D-dimer cutoff points of 2.6, 1.1, and 1.1 microg/mL for the low-, moderate- and high-risk PTP groups, respectively. In the low-risk PTP group, specificity increased from 48.9% to 78.2% (P < .0001) with use of the different D-dimer cutoff value. In the moderate- and high-risk PTP groups, however, the different D-dimer levels did not achieve substantial improvement. Despite this, the overall use of venous DU scanning could have been reduced by 43.0% (381 of 886) if the different D-dimer cutoff points had been used.

CONCLUSIONS

Combination of a specific D-dimer level with the clinical probability score is most effective in low-risk PTP patients for excluding DVT. In moderate- and high-risk PTP patients, however, the recommended cutoff points of 1.0 microg/mL may be preferable. These results show that different D-dimer levels for patients differing in risk is feasible for excluding DVT using the latex agglutination D-dimer assay.

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.

The value of D-dimer in the detection of early deep-vein thrombosis after total knee arthroplasty in Asian patients: a cohort study

Background and purpose

The relationship of D-dimer and deep-vein thrombosis (DVT) after total knee arthroplasty (TKA) remains controversial. The purpose of this study was to assess the value of D-dimer in the detection of early DVT after TKA.

Methods

The measurements of plasma D-dimer level were obtained preoperatively and at day 7 postoperatively in 78 patients undergoing TKA. Ascending venography was performed in 7 to 10 days after surgery. The plasma D-dimer levels were correlated statistically with the venographic DVT.

Results

Venographic DVT was identified in 40% of patients. High plasma D-dimer level >2.0 μg/ml was found in 68% of patients with DVT and 45% without DVT (P < 0.05). Therefore, high D-dimer level greater than 2.0 μg/ml showed 68% sensitivity, 55% specificity, 60% accuracy, 50% positive predictive rate and 72% negative predictive rate in the detection of early DVT after TKA.

Conclusion

High plasma D-dimer level is a moderately sensitive, but less specific marker in the detection of early of DVT after TKA. Measurement of serum D-dimer alone is not accurate enough to detect DVT after TKA. Venography is recommended in patients with elevated D-dimer and clinically suspected but asymptomatic DVT after TKA.

Painful swollen leg--think beyond deep vein thrombosis or Baker's cyst

BACKGROUND

The diagnosis of deep vein thrombosis of leg is very common in clinical practice. Not infrequently a range of pathologies are diagnosed after excluding a thrombosis, often after a period of anticoagulation.

CASE PRESENTATION

This is a report of three patients who presented with a painful swollen leg and were initially treated as a deep vein thrombosis or a baker's cyst, but later diagnosed as a pleomorphic sarcoma, a malignant giant cell tumor of the muscle and a myxoid liposarcoma. A brief review of such similar reports and the relevant literature is presented.

CONCLUSION

A painful swollen leg is a common clinical scenario and though rare, tumors must be thought of without any delay, in a duplex negative, low risk deep vein thrombosis situation.

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.

D-dimer concentration increases with age reducing the clinical value of the D-dimer assay in the elderly

BACKGROUND

The D-dimer assay is used as an exclusion test in the assessment of suspected venous thromboembolic disease; patients with a negative result have a low probability of thrombosis. We reviewed the D-dimer results from a hospital and community laboratory using the vidas D-dimer test to assess the influence of age on the D-dimer assay.

METHODS

D-dimer results from 6631 unselected patients aged more than 16 years were analysed in four age groups and it was shown that the median D-dimer concentration increased with age (16-40 years, 294 ng/mL; 40-60 years, 387 ng/mL; 60-80 years; 854 ng/mL; >80 years, 1397 ng/mL). To test the effect of age on the assay specificity, a cohort of 1897 patients with suspected venous thromboembolic disease was analysed separately. Patients with a negative D-dimer were discharged without further investigation. Patients with a positive result and a clinical suspicion of thrombosis underwent further investigation. One hundred and sixty-five deep vein thrombosis or pulmonary embolus cases were identified.

RESULTS

The assay specificity decreased with age from 70% in patients less than 40 years to below 5% in patients more than 80 years. Receiver operator curves were prepared for each age group and the effect of altering the threshold value was analysed. In patients 60-80 years old a threshold value of 1000 ng/mL increased assay specificity to 55% without loss of assay sensitivity.

CONCLUSION

The vidas D-dimer assay with a threshold value of 500 ng/mL has little clinical value as an exclusion test in patients more than 80 years old. The assay specificity is poor (26%) in patients aged 60-80 years but could be improved by increasing the threshold value to 1000 ng/mL. We believe that this should be tested in a prospective trial.

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.

Does an immunochromatographic D-dimer exclude acute lower limb deep venous thrombosis?

BACKGROUND

A pre-test probability score and D-dimer may reduce the need for ultrasound examinations for excluding lower limb deep venous thrombosis (DVT).

OBJECTIVE

To establish the accuracy of an immunochromatographic D-dimer assay called 'Simplify' for diagnosis of acute DVT by complete (calf veins included) lower limb ultrasound examination.

METHODS

A total of 453 consecutive patients presented to the ED of a tertiary centre with suspected first episode of DVT, were prospectively recruited. A pre-test probability score (Hamilton Score), an immunochromatographic D-dimer and a complete, single, unilateral lower limb ultrasound examination were performed in all patients. All patients with a negative ultrasound examination were followed up for 3 months.

RESULTS

There were 159 men and 294 women with a mean age of 55.8 years (SD 20.3). Of the 227 patients with a negative D-dimer, 214 patients had negative ultrasound examinations and 13 patients had isolated calf DVT. Among the 226 patients with a positive D-dimer, 74 patients had DVT and 152 patients had negative ultrasound examinations. The sensitivity, specificity, positive and negative predictive values were 85.1% (75.8-91.8), 58.5% (53.4-63.5), 32.7% (26.6-38.9) and 94.3% (90.4-96.9), respectively. One hundred and sixty-five patients had an unlikely Hamilton Score and a negative D-dimer. The negative predictive value of the immunochromatographic D-dimer in an unlikely Hamilton Score population was 98.8% (95.7-99.8%).

CONCLUSION

An unlikely probability Hamilton Score and a negative immunochromatographic D-dimer reliably exclude both proximal and isolated calf DVT.

Diagnosis of lower limb deep venous thrombosis in emergency department patients: performance of Hamilton and modified Wells scores

STUDY OBJECTIVE

We validate and compare the Hamilton score for assessment of lower limb deep venous thrombosis with the modified Wells score.

METHODS

Consecutive patients presenting to the emergency department of a tertiary center for suspected lower limb deep venous thrombosis were prospectively recruited. Hamilton score and modified Wells score calculations, D-dimer, and complete (calf veins included), single lower limb ultrasonographic examination were performed for all patients. All patients with a negative ultrasonographic examination result for deep venous thrombosis were followed up for 3 months.

RESULTS

The study population consisted of 116 men and 193 women, with an average age of 55.6 years (SD 20.1). A total of 67 (21.7%) patients were diagnosed with deep venous thrombosis. Forty (59.7%) of these patients had isolated calf deep venous thrombosis, and the other 27 (40.3%) patients had proximal deep venous thrombosis. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) for an unlikely Hamilton score (score < or = 2) and D-dimer were 99% (95% confidence interval [CI] 92% to 99.96%), 42 % (95% CI 36% to 49%), 32% (95% CI 26% to 39%), 99% (95% CI 95% to 99.98%), 1.7 (95% CI 1.52% to 1.9%), and 0.04 (95% CI 0.01 to 0.25), respectively. The sensitivity, specificity, PPV, NPV, LR+ and LR- for an unlikely modified Wells score (score < or = 1) and D-dimer were 99% (95% CI 92% to 99.96%), 33 % (95% CI 27% to 39%), 29% (95% CI 23% to 35%), 99% (95% CI 93% to 99.97%), 1.47 (95% CI 1.34 to 1.62), and 0.05 (95% CI 0.01 to 0.32), respectively.

CONCLUSION

An unlikely probability of Hamilton score and a negative D-dimer may effectively exclude a lower limb deep venous thrombosis. Hamilton and modified Wells scores have similar performance characteristics.

Importance of Pretest Probability Score and D-Dimer Assay Before Sonography for Lower Limb Deep Venous Thrombosis

OBJECTIVE

The purpose of our study was to develop and validate a clinical score (the Hamilton score) for the assessment of lower limb deep venous thrombosis (DVT) and to determine the usefulness of this score and a D-dimer assay before a complete lower limb sonographic examination.

SUBJECTS AND METHODS

Five hundred forty-two consecutive ambulatory patients presenting to the emergency department were prospectively recruited, of whom 16 patients were excluded from the study. Eighteen history and examination variables were collected by the emergency department physicians. The Simplify D-dimer assay and a complete, single lower limb sonographic examination were performed in all patients. All patients with a negative sonographic examination for DVT were followed up for 3 months, and all those with a positive sonographic examination were given anticoagulation therapy. The Hamilton score was developed using the data from the first 214 patients and was prospectively validated in the next 312 patients.

RESULTS

The most significant factors associated with a diagnosis of DVT were immobilization of the lower limb, active malignancy, and a strong clinical suspicion of DVT without other diagnostic possibilities by the emergency department physicians. Other factors were bed rest or recent surgery, male sex, calf circumference difference greater than 3 cm, and erythema. The Hamilton score was developed with the following weights: immobilization of the lower limb (2 points), active malignancy (2 points), strong clinical suspicion of DVT without other diagnostic possibilities by the emergency physicians (2 points), bed rest or recent surgery (1 point), male sex (1 point), calf circumference difference greater than 3 cm (1 point), and erythema (1 point). A score of 3 or greater indicates a likely probability for DVT, and a score of 2 or less represents an unlikely probability for DVT. Of the 103 patients with an unlikely probability Hamilton score and a negative D-dimer assay, only one patient had isolated calf DVT. A combined diagnostic strategy of unlikely-probability Hamilton score and a negative D-dimer would have a negative predictive value of 99% (95% confidence interval, 94.7-100%).

CONCLUSION

An unlikely-probability Hamilton score and a negative Simplify D-dimer assay effectively exclude lower limb DVT, and a sonographic examination is unnecessary in this group of ambulatory emergency department patients.

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.

Management studies using a combination of D-dimer test result and clinical probability to rule out venous thromboembolism: a systematic review

BACKGROUND

While the number of patients with suspected venous thromboembolism (VTE) referred to hospital emergency units increases, the proportion in whom the diagnosis can be confirmed is decreasing. A more efficient but safe diagnostic strategy is needed.

OBJECTIVE

To evaluate the safety of withholding anticoagulant therapy in patients suspected of VTE based on a diagnostic work-up that combines a clinical decision rule (CDR) with a D-dimer test result without performing additional diagnostic tests.

PATIENTS/METHODS

We searched Medline (January 1996-December 2004)-related articles and reference lists of studies in English for prospective clinical studies that managed consecutive patients suspected of VTE and used a D-dimer assay combined with an explicit CDR or implicit clinical judgment.

RESULTS

We identified 11 studies in which 6837 consecutive outpatients suspected of VTE were included. In the combined management studies, the overall rate of thromboembolic events was nine out of 2056 patients (0.44 %, 95% CI 0.2%-0.83%) in whom anticoagulants were withheld based on the D-dimer result and a low clinical score. Similar results were obtained with qualitative and quantitative D-dimer tests and with different decision rules. The rate of exclusion varied between 30% and 50% and was highest with a low incidence of VTE among those referred.

CONCLUSION

Withholding anticoagulant treatment in patients suspected of VTE on the basis of a work-up consisting of a low clinical probability combined with either a qualitative or quantitative D-dimer test result is safe.

Determinants of plasma D-dimer levels in a traveling population

BACKGROUND

Plasma D-dimer measurement is a widely used diagnostic test for assessing individuals with suspected venous thromboembolism (VTE). Whilst a negative test is helpful in ruling out thrombosis, the significance and determinants of an elevated plasma D-dimer level in otherwise healthy subjects are poorly understood.

OBJECTIVES

To determine the association between recognized risk factors for VTE and plasma D-dimer levels in an adult population.

SUBJECTS AND METHODS

Blood samples for measurement of plasma D-dimer levels were obtained from 1000 adults aged <70 years who were participating in a study investigating the incidence of VTE in long distance air travellers. The relationship between D-dimer levels and selected risks factors for VTE including thrombophilia status was investigated.

RESULTS

The median (Inter-quartile range) D-dimer level was 243 ng mL(-1) (175-345). Multivariate analysis showed that plasma D-dimer levels were positively associated with increasing age, larger body mass index, female gender, the use of hormone therapy, thrombophilia state, and the presence of co-morbid conditions.

CONCLUSION

Plasma D-dimer levels vary markedly between individuals and are associated with known risk factors for VTE, including the presence of thrombophilia conditions. The potential role for the measurement of plasma D-dimer as a marker for thrombosis risk requires further investigation.

Point-of-care immunotesting: Approaching the analytical performance of central laboratory methods

The use of point-of-care (POC) immunoassays has increased significantly and the menu of analytes continues to expand. Most of the rapid immunoassays are currently based on simple manual assay devices such as the immunochromatographic, agglutination, and immunofiltration assays. Although automated readers have recently been introduced at an increasing pace, the major benefit of these genuinely hand-portable assay devices is that they do not usually necessitate instrumentation but can be performed anywhere. Significant advances in assay and detection technologies have, however, recently facilitated the introduction of truly quantitative, sophisticated immunoassay methods to POC settings as well, with the analytical performance characteristics approaching those of conventional laboratory assays. Furthermore, innovative assay technologies such as those based on immunosensors have been introduced to POC testing (POCT) without ever being employed in clinical laboratories. However, further simplification of the assay procedures and analyzers is still feasible, and strong efforts are directed towards the development of miniaturized and simple, yet sensitive and quantitative, novel assay technologies to keep up with the increasing expectations set on future POC immunotesting.

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.

Extended versus rapid analysis of the leg vein system: a multicenter ultrasound study (the ERASMUS study)--an interim analysis

The reliability of diagnostic strategies based on compression ultrasonography (CUS) for the diagnosis of proximal deep venous thrombosis (DVT) in symptomatic (out)patients is well documented; however these approaches never gained widespread application.Echo-color-Doppler (ECD), is regularly adopted by vascular laboratories as first line test in case of clinically suspected DVT, although the specificity of calf veins imaging is uncertain, as is the negative predictive value of a normal ECD workup. To date, no direct comparison of these strategies is available in the literature. We designed a randomised prospective study to compare the safety and feasibility of two diagnostic approaches: a "rapid" (CUS + D-dimer), and an "extended" strategy (ECD of the whole-leg). All consecutive patients with suspected symptomatic DVT of the legs, if at their first episode, and if not meeting exclusion criteria, will be enrolled in the study. The primary outcome of the study will be the rate of symptomatic VTE during a 3-month follow-up, after a normal diagnostic workup with either of the two proposed strategies. All events will be adjudicated by a blind and independent committee, based on the results of objective testing. An interim data analysis will be presented during the congress session.

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.

D-dimer testing for deep venous thrombosis: a metaanalysis

BACKGROUND

The use of D-dimer assays as a rule-out test for deep venous thrombosis (DVT) is controversial. To clarify this issue we performed a systematic review of the relevant literature.

METHODS

We identified eligible studies, using MEDLINE entries from February 1995 through October 2003, supplemented by a review of bibliographies of relevant articles. Studies reporting accuracy evaluations comparing D-dimer test results with lower extremity ultrasound or venography in symptomatic patients with suspected acute DVT were selected for review. Two reviewers critically appraised each study independently according to previously established methodologic standards for diagnostic test research. Those studies judged to be of highest quality were designated Level 1.

RESULTS

The 23 Level 1 studies reported data on 21 different D-dimer assays. There was wide variation in assay sensitivity, specificity, and negative predictive values, and major differences in methodology of reviewed studies. A multivariate analysis of assay performance, controlling for sample size, DVT prevalence, reference standard, and patient mix, found few differences among the assays in effect on test performance as measured by diagnostic odds ratio. Increasing prevalence of DVT was associated with poorer test performance (P = 0.01), whereas the choice of venography as the reference standard was associated with better test performance (P <0.005).

CONCLUSIONS

Explanations for the wide variation in assay performance include differences in biochemical and technical characteristics of the assays, heterogeneity and small size of patient groups, and bias introduced by choice of reference standards. Assay sensitivity and negative predictive value were frequently <90%, uncharacteristic of a good rule-out test. General use of D-dimer assays as a stand-alone test for the diagnosis of DVT is not supported by the literature.

Real-time B-mode ultrasound in the ED saves time in the diagnosis of deep vein thrombosis (DVT)

We hypothesize that EPs can decrease the time to disposition when performing examinations for deep venous thrombosis (DVT) compared with disposition times using imaging specialists (IS). We performed a prospective, single-blind observational study at an academic ED over the course of 1 year. Patients were enrolled based on study physician availability. EPs ordered the corroborative ultrasound, then performed their own examination. EPs recorded patient triage time, ED results, and disposition times for both EP and IS departments. One hundred fifty-six patients were enrolled. Thirty-four (22%) were diagnosed with a DVT. Mean time from triage to EP disposition was 95 minutes and mean time from triage to radiology disposition was 220 minutes. The difference of 125 minutes was statistically significant (P <.0001). EPs and ISs had excellent agreement (kappa = 0.9). Compression ultrasound performed by EPs resulted in a significant decreased time to disposition. Agreement with ISs was excellent.

Venous protocols, techniques, and interpretations of the upper and lower extremities

Deep venous thrombosis and pulmonary embolism are common problems and frequently included in the differential diagnosis of patients presenting to the emergency department and in the acute care setting. Clinical signs and symptoms of these entities are nonspecific and it is important to perform objective testing to confirm the diagnosis and initiate proper therapy. Compression ultrasonography is the diagnostic procedure of choice for the investigation of patients with suspected deep venous thrombosis. This article reviews the clinical indications, diagnostic techniques, and interpretation of compression ultrasound to assess deep venous thrombosis in the upper and lower extremities and to evaluate the role of compression ultrasonography in the assessment of patients with suspected pulmonary embolism.

Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis

BACKGROUND

Several diagnostic strategies using ultrasound imaging, measurement of D-dimer, and assessment of clinical probability of disease have proved safe in patients with suspected deep-vein thrombosis, but they have not been compared in randomized trials.

METHODS

Outpatients presenting with suspected lower-extremity deep-vein thrombosis were potentially eligible. Using a clinical model, physicians evaluated the patients and categorized them as likely or unlikely to have deep-vein thrombosis. The patients were then randomly assigned to undergo ultrasound imaging alone (control group) or to undergo D-dimer testing (D-dimer group) followed by ultrasound imaging unless the D-dimer test was negative and the patient was considered clinically unlikely to have deep-vein thrombosis, in which case ultrasound imaging was not performed.

RESULTS

Five hundred thirty patients were randomly assigned to the control group, and 566 to the D-dimer group. The overall prevalence of deep-vein thrombosis or pulmonary embolism was 15.7 percent. Among patients for whom deep-vein thrombosis had been ruled out by the initial diagnostic strategy, there were two confirmed venous thromboembolic events in the D-dimer group (0.4 percent; 95 percent confidence interval, 0.05 to 1.5 percent) and six events in the control group (1.4 percent; 95 percent confidence interval, 0.5 to 2.9 percent; P=0.16) during three months of follow-up. The use of D-dimer testing resulted in a significant reduction in the use of ultrasonography, from a mean of 1.34 tests per patient in the control group to 0.78 in the D-dimer group (P=0.008). Two hundred eighteen patients (39 percent) in the D-dimer group did not require ultrasound imaging.

CONCLUSIONS

Deep-vein thrombosis can be ruled out in a patient who is judged clinically unlikely to have deep-vein thrombosis and who has a negative D-dimer test. Ultrasound testing can be safely omitted in such patients.

The usefulness of five D-dimer assays in the exclusion of deep venous thrombosis

D-Dimer measurement is a promising tool in the exclusion of venous thrombosis. New d-dimer assays have been introduced, but need clinical validation. Our objective was to evaluate the clinical usefulness of four relatively new d-dimer assays and a classical ELISA in outpatients suspected for deep venous thrombosis. In 537 patients, participants in a large prospective management study using a clinical probability score and a d-dimer measurement (Tina-quant), additional samples were taken for d-dimer measurement using the Asserachrom ELISA, the VIDAS New, the STA-LIA and the Miniquant assay. Performances of each test were calculated using clinical data during a 3-month follow-up. Thrombosis was detected in 224 patients (42%). The area under the ROC curve was significantly higher for the Tina-quant as compared to the other assays. Using standard cut-off values, sensitivity, negative predictive value (NPV) and specificity of the Asserachrom were 97, 94 and 33%, respectively. For the VIDAS New, values were 100, 96 and 8%, respectively. The Tina-quant showed values of 99, 98 and 41%, respectively, and the STA-LIA 98, 95 and 32%. Values for the Miniquant were 95, 94 and 52%. The d-dimer assays in our study all show a high sensitivity and negative predictive value, but none of the assays reached an NPV of > 98% at standard cut-off values. d-Dimer assays with a low specificity still necessitate additional diagnostic tests in the majority of the patients.

The d-dimer test for deep venous thrombosis: gold standards and bias in negative predictive value

BACKGROUND

Because venous ultrasound (US) fails to fully image the calf veins, there is the potential for US gold standard studies to classify patients with calf deep venous thrombosis (DVT) in the nondiseased category, causing bias in test index calculations. A false increase in negative predictive value (NPV) is especially likely because calf DVT false-negative tests will be counted in the numerator along with the true-negative tests in NPV calculations. We verified the presence and magnitude of this bias for the d-dimer test.

METHODS

We abstracted data on overall (calf and thigh) and thigh-only test sensitivity, specificity, and NPV from the six English language studies published between March 1995 and October 2001 that compared d-dimer to a gold standard (GS) capable of imaging both thigh and calf veins and that also stratified results by thigh and calf location. Thigh specificity and NPV were calculated classifying calf DVT patients as free of disease.

RESULTS

The six studies included 81-214 participants and provided 26 comparisons of 16 different d-dimer assays to the GS. Thigh sensitivity was higher than overall sensitivity in 22 of 26 comparisons (range, -0.3 to 8.6); thigh specificity was lower than overall specificity in all comparisons (range, -0.7 to -7.8); and thigh NPV was higher than overall NPV in 22 of 26 comparisons and unchanged in 4 comparisons (range, 0.0-9.2). NPV was >95% in 20 of the thigh results but >95% in only 8 of the overall results.

CONCLUSIONS

Different GS can produce clinically significant differences in test indices. Care must be taken in interpreting DVT studies that evaluate d-dimer as a rule-out test and that use US as a GS, because missed calf DVT can falsely increase the NPV.

Comparative evaluation of d-dimer assays for exclusion of deep venous thrombosis in symptomatic outpatients

Diagnostic work-up of patients sent to the hospital for diagnosing of deep venous thrombosis (DVT) often combines the determination of D-dimer and the application of a clinical probability score. To fulfill diagnostic as well as economic needs, D-dimer assays should exhibit a high negative predictive value (NPV) as well as reasonable specificity. In this study, we evaluated both a latex-enhanced immunoassay for use on routine coagulation analyzers and a radial partition immunoassay (RPIA) for use on a point-of-care analyzer. Samples included were from 344 outpatients with suspected deep venous thrombosis. Among them, 100 had deep venous thrombosis. Results obtained for both assays show a good efficiency for exclusion of deep venous thrombosis with well-acceptable specificity.

Diagnostic value of d-dimer in patients with a moderate pretest probability of deep venous thrombosis

The negative predictive value (NPV) of d-dimer (DD) for the exclusion of venous thromboembolism is, overall, high and tends to increase as clinical pretest probability decreases. We have assessed the accuracy of a diagnostic protocol including clinical evaluation and DD in 134 outpatients presenting with a moderate pretest probability of proximal deep venous thrombosis (DVT). In these patients, a negative DD value safely excluded DVT (NPV 100%, 95% CI 85-100) In our experience, these results are equivalent to those found for low-pretest probability patients and therefore the same diagnostic strategy can be used for both risk groups.

[Diagnostic value of D-dimer in patients with a low pretest probability of deep venous thrombosis of lower extremities]

BACKGROUND

We aimed to assess the accuracy of a diagnostic strategy including broth clinical assessment and determination of D-dimer (DD) in patients with clinically suspicion of low pretest probability of deep venous thrombosis (DVT).

METHOD

149 outpatients (mean age 69; SD 16) with clinically suspected proximal DVT attending our Emergency Department and classified as low pretest probability were included in an observational prospective study. In patients with a DD (STA Liatest D-Di, Diagnostica Stago, Asnières sur Seine, France) concentration below the cut-off value (0.4 ng/ml) the diagnosis of DVT was readily ruled out, whereas those individuals with a positive DD result underwent compression Doppler venous ultrasound. A 3-month clinical follow-up was carried out in those patients in whom a diagnosis of DVT was initially excluded.

RESULTS

Only 2 cases of DVT were confirmed (prevalence 1.3%; CI 95%, 0.2-5.3). In 47.6% of cases, a DD negativity ruled out the diagnosis of DVT. The rate of negative DD results was significantly lower in patients below 70 years of age as compared to older patients (73.6 versus 33.3%) (p < 0.001). Sensitivity, specificity, positive predictive value and negative predictive value of DD in our series were 100% (CI 95%,19.7-95.1), 48.3% (CI 95%, 40.0-56.7), 2.6% (CI 95%, 0.4-9.8) and 100% (CI 95%, 93.6-99.8) respectively, the latter being similar in the two age groups. No case of DVT was diagnosed during the follow-up period.

CONCLUSIONS

In patients with a low pretest probability of DVT a negative DD result reliably and safely rules out such diagnosis. However, the diagnostic value of DD is lower in elderly patients (>= 70 years of age) due to a lower rate of negative results in these individuals.