Comparison of various D-dimer tests for the diagnosis of deep venous thrombosis

D-Dimer Testing: Laboratory Aspects and Current Issues

D-dimer has become one of the commonly requested coagulation tests, especially in the venous thromboembolism rule out setting. Appropriate D-dimer testing has significantly decreased the number of radiological investigations in this clinical scenario. D-dimer testing also plays an important role in the diagnostic process of the systemic coagulation disorders, especially disseminated intravascular coagulation in conjunction with other coagulation tests. However, widespread D-dimer testing without good understanding of the technical issues related to the test has recently caused some concerns. This review aims to address the basic physiology of D-dimer formation, the different methods available for its routine assessment, the current problems that both clinicians and laboratory scientists face with this test, and the important need for harmonization of commercial immunoassays.

Endothelial dysfunction in Buerger's disease and its relation to markers of inflammation

BACKGROUND

Buerger's disease (BD) is a segmental occlusive vascular disease. The aim of this study was to detect functional changes in brachial artery and asymptomatic morphological changes in extra-cranial carotid arteries not affected by the disease process and to assess markers of inflammation and endothelial damage.

MATERIALS AND METHODS

Fourteen patients in the remission phase of BD and the same number of age- and sex-matched healthy controls were included in the study. The capability of endothelium-dependent (flow-mediated) and endothelium-independent dilation of the brachial artery and intima-media thickness of the carotid arteries were measured using high-resolution ultrasound. Laboratory parameters of endogenous fibrinolytic activity, inflammation and endothelial dysfunction were also measured.

RESULTS

Patients with BD had a diminished capability of endothelium-dependent vasodilation and higher levels of some circulating markers of inflammation, such as leukocytes, C-reactive protein, intercellular adhesion molecule-1 and E-selectin. Intercellular adhesion molecule-1 levels were related to some of the inflammatory markers (sedimentation rate, C-reactive protein, alpha2-globulins and fibrinogen), while E-selectin was correlated with decreased endogenous blood fibrinolytic activity. Endothelium-dependent vasodilation was in negative correlation with the relative share of neutrophil granulocytes. There were no significant differences in intima-media thickness between patients with BD and controls.

CONCLUSIONS

Our study has expressed generalized functional arterial disorder in patients with BD not accompanied by any measurable morphological changes of the carotid arterial wall. Functional deterioration of brachial artery could be related to increased levels of various inflammatory markers--the process which is most probably the basic pathogenetic mechanism of the disease.

The use of a fixed high sensitivity to evaluate five D-dimer assays' ability to rule out deep venous thrombosis: a novel approach

Suspected deep venous thrombosis (DVT) is difficult to refute without complex diagnostic algorithms and expensive testing. We analysed five D-dimer assays' utility for exclusion of suspected DVT during a prospective clinical cohort trial, choosing a highly sensitive cut-off value at which to compare the assays. Assays were performed on 436 consecutive patients who were referred with symptoms that suggested a first episode of DVT. Venous thromboembolism (VTE) was defined as positive findings on comprehensive duplex ultrasonography or any episode, or complication of VTE detected during 3 months of clinical follow-up. All five assays were performed in 377 patients. At a highly sensitive cut-off value, all five assays reliably excluded DVT in the study population. While the choice of a highly sensitive cut-off value reduced the specificity of all the assays, the change in specificity differed between tests. Our findings suggest that a second-generation D-dimer assay could be used as a stand-alone test to rule out suspected DVT when a highly sensitive cut-off value is chosen. These findings should be subjected to a prospective management study, as a small reduction in sensitivity from our findings could result in a clinically relevant decrease in negative predictive value.

The performance of quantitative D-dimer assays in laboratory routine

Assessment of D-dimer in plasma is routinely used for the exclusion of venous thrombosis and the monitoring of hypercoagulability. Little information is available about the performance of D-dimer assays in clinical laboratories examined by external quality assessment schemes. We obtained results from 423 laboratories measuring plasma pools from patients with elevated D-dimer levels mixed with human normal plasma. The results from five samples were reported containing D-dimer from the lower normal range up to a 20-fold increased level. In addition, information about the assignment of a cut-off point and the medical need to apply these assays was obtained by standardized questionnaire. Participants reported results and additional information from 20 different assays. Lack of standardization regarding the calibration concepts obstructs comparability of results. Results in one sample varied up to 20-fold between the assays applied. In addition, a high variability was reported around the cut-off values introduced for the exclusion of venous thrombosis and pulmonary embolism. As a consequence, generally accepted cut-off values cannot be established. For cut-off assignment, 62% of participants used the kit insert but also 14% used local validation. In conclusion, standardization or at least harmonization of D-dimer assays is necessary to ensure comparability of D-dimer plasma levels measured in clinical routine.

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.

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.

A new rapid bedside assay for quantitative testing of D-Dimer (Cardiac D-Dimer) in the diagnostic work-up for deep vein thrombosis

The accuracy of a new bedside, rapid and quantitative D-Dimer assay (Cardiac D-Dimer) was evaluated in outpatients with clinically suspected deep vein thrombosis (DVT); VIDAS test was used as reference method. Eighty consecutive outpatients with suspected DVT of a lower limb were included in the study. Patients were classified as DVT positive or negative according to results of objective test (serial CUS), pretest clinical probability and 3-month follow-up. DVT was diagnosed in 32/80 patients (40%). The performance of the two D-Dimer assays was comparable, as indicated by the areas under the ROC curves (0.89 and 0.88, for Cardiac D-Dimer and VIDAS, respectively) and the coefficient of correlation (r=0.91). The reproducibility of the test was acceptable (from 6.2% to 12.0%). The sensitivity and negative predictive values were 100% for both tests. The specificity (SP) and positive predictive values (PPV) were similar (SP: 50.0% and 52.0%, PPV: 57.1% and 58.2%, for Cardiac D-Dimer and VIDAS, respectively). The Cardiac D-Dimer test proved to be very accurate and produced results fully comparable to those obtained with the VIDAS test. Since the test can be directly performed in the emergency room within a few minutes, it seems to have great clinical potential. The place of this assay in the diagnostic strategy of DVT remains to be determined in prospective management studies.

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.

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.

Combination of a normal D-dimer concentration and a non-high pretest clinical probability score is a safe strategy to exclude deep venous thrombosis

BACKGROUND

Serial ultrasonography is reliable for the diagnosis of deep venous thrombosis in symptomatic patients, but the low prevalence of thrombosis in this group renders the approach costly and inconvenient to patients. We studied the clinical validity of the combination of a pretest clinical probability score and a D-dimer test in the initial evaluation of patients suspected of deep venous thrombosis.

METHODS AND RESULTS

Patients with a normal D-dimer concentration (<500 fibrin equivalent units [FEU] microg/L) and a non-high probability score (<3) had no further testing. Patients with a normal D-dimer concentration and a high probability score (> or =3) underwent one ultrasonogram. Serial ultrasonography was performed in patients with an abnormal D-dimer concentration. Patients were followed for 3 months. A total of 812 patients were evaluable for efficacy. Only 1 of 176 patients (0.6%; 95% CI, 0.02% to 3.1%) with a normal D-dimer concentration and a non-high probability score developed thrombosis during follow-up. A normal D-dimer concentration and a high probability score were found in 39 patients; 3 of them (7.7%; 95% CI, 1.6% to 20.9%) had thrombosis at presentation, and one (2.8%; 95% CI, 0.07% to 14. 5%) developed pulmonary embolism during follow-up. In 306 of 597 patients (51.3%) with an abnormal D-dimer concentration, thrombosis was detected by serial ultrasonography. Six patients (2.1%; 95% CI, 0.8% to 4. 4%) developed thrombosis during follow-up. No deaths due to thromboembolism occurred during follow-up. The total need for ultrasonography was reduced by 29%.

CONCLUSION

The combination of a non-high pretest clinical probability score and a normal D-dimer concentration is a safe strategy to rule out deep venous thrombosis and to withhold anticoagulation.

Changes in LPIA D-dimer levels after total hip or knee arthroplasty relevant to deep-vein thrombosis diagnosed by bilateral ascending venography

The purpose of the current retrospective study was to determine the most sensitive and specific cutoff value of plasma D-dimer level associated with deep-vein thrombosis (DVT) after total hip (THA) or knee (TKA) joint arthroplasty. Diagnosis of DVT was determined by bilateral ascending venography pre- and postoperatively. Plasma D-dimer levels were measured by a latex photometric immunoassay system (LPIA) preoperatively and postoperatively on days 1, 3, 7, 10, 14, and 21. Postoperative DVT diagnosed by venography was found in 22 patients (40.1%) after THA and in 18 patients (64.3%) after TKA. Plasma D-dimer levels were significantly higher ( P < 0.01) in patients with DVT than in those without DVT on days 1, 7, and 10 after THA, but only on day 7 after TKA. Statistical analysis confirmed that a cutoff value of 10.0 microg/ml for D-dimer on day 7 was most sensitive (THA, 95.5%; TKA, 94.4%) and most specific (THA, 96.9%; TKA, 90.0%) in the diagnosis of DVT after THA as well as TKA. It was concluded that over 10 microg/ml of LPIA D-dimer on postoperative day 7 appears to be an indication of the occurrence of DVT after THA and TKA.

Validity of D-dimer tests in the diagnosis of deep vein thrombosis: a prospective comparative study of three quantitative assays

OBJECTIVES

To assess the diagnostic reliability of a new quantitative D-dimer assay (VIDAS New) and an established quick test (Nycocard D-dimer assay) in the diagnosis of deep vein thrombosis (DVT) compared with ultrasonography. A third assay (Auto Dimer) became available during sample collection and has been included in the final assessment. The diagnostic performance of the Auto Dimer assay was evaluated on three different coagulation analysers.

DESIGN

A clinical prospective study of patients admitted to hospital for evaluation of DVT. Setting. The admission ward at Aalborg Hospital. Subjects. A total of 113 outpatients with suspected DVT. Main outcome measures. Compression ultrasonography was used as the reference method for a diagnosis of DVT and compared with different D-dimer assays. The results were expressed as sensitivity, specificity, positive predictive value and negative predictive value (NPV).

RESULTS

Deep vein thrombosis was established in 49 patients (43%). Two D-dimer assays (VIDAS New and Auto Dimer) showed sensitivities of 90 and 88%, specificities of 42 and 44%, and NPV's of 85 and 83%, respectively. The Nycocard D-dimer assay showed a sensitivity of 63%, specificity of 67% and NPV of 71%.

CONCLUSIONS

The diagnostic performance of VIDAS New and the Auto Dimer D-dimer assays is almost identical, but this study suggests that neither of the D-dimer assays is suitable as the only screening method for DVT, in a situation with a high pretest probability of DVT. This call for a differential strategy that distinguishes between cases of low and high clinical probability using either a D-dimer test or ultrasonography. Abbreviations DVT, deep venous thrombosis, NPV, negative predictive value, PPV, positive predictive value

Usefulness of a semiquantitative D-dimer test for the exclusion of deep venous thrombosis in outpatients

PURPOSE

The D-dimer test is used commonly in diagnostic strategies to reduce the need for ultrasonography in patients suspected of having deep venous thrombosis. We studied several clinical and laboratory variables that might limit the accuracy of a semiquantitative D-dimer test.

SUBJECTS AND METHODS

In this retrospective cohort study, 704 outpatients suspected of having deep venous thrombosis underwent a semiquantitative D-dimer test and ultrasonography. The performance of the D-dimer test was calculated in patients using anticoagulants (n =61), patients with previous thrombosis (n =127), and patients with malignancy (n =47), including 39 patients with more than one of these characteristics. The 508 remaining patients were considered to be the reference group.

RESULTS

A total of 254 patients (36%) had evidence of deep venous thrombosis. The D-dimer test had a sensitivity of 99% (174/176; 95% confidence interval [CI]: 96% to 100%) and a negative predictive value of 98% (98/100; 95% CI: 93% to 100%) in the reference group. The sensitivity of the D-dimer test in patients using oral anticoagulants was 75% (6/8; 95% CI: 35% to 97%; P =0.01 compared with the reference group). Test sensitivity was 96% (51/53; 95% CI: 87% to 100%) in patients with previous thrombosis, and 100% (29/29; 95% CI: 88% to 100%) in patients with cancer. However, 553 (79%) of all patients, including 43 of the cancer patients (91%), had an abnormal D-dimer test.

CONCLUSION

The semiquantitative D-dimer test in this study has a high sensitivity and negative predictive value in the exclusion of deep venous thrombosis, except perhaps among patients using oral anticoagulants. D-dimer tests in patients with cancer and in patients over 70 years old may not be worthwhile, because the tests are usually positive.