Rapid Quantitative D-dimer Assay and Clinical Evaluation for the Diagnosis of Clinically Suspected Deep Vein Thrombosis

Referent d-dimer enzyme-linked immunosorbent assay testing is of limited value in the exclusion of thromboembolic disease: result of a practical study in an ED

OBJECTIVE

The aim of this study was to assess in clinical practice the accuracy of a referent d-dimer enzyme-linked immunosorbent assay for the exclusion of venous thromboembolic disease (VTED).

PATIENTS AND METHODS

An observational prospective study took place in an emergency department; 205 consecutive outpatients suspected of having VTED were included. Blood samples were collected at admission for VIDAS DD measurement. Venous thromboembolic disease was confirmed by standard clinical imaging. All patients were followed up at 3 months.

RESULTS

Venous thromboembolic disease was confirmed in 57 patients (28%). The sensitivity and negative predictive value of a DD assay lower than 500 ng/mL were 78% (95% confidence interval = 67%-87%) and 84% (95% confidence interval = 73%-90%), respectively. Twelve patients had a false-negative DD with one or more of the following: (a) symptoms reported for more than 15 days (n = 2), (b) prior anticoagulation (n = 3), (c) distal VTED (n = 5), or (d) high clinical probability (n = 3).

CONCLUSION

In our cohort of patients, DD was less accurate than previously reported, with an upper estimate of the sensitivity of only 87%.

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.

Performance of the automated and rapid STA Liatest D-dimer on the STA-R analyzer

OBJECTIVE

The aim of the present study was to investigate the accuracy indices of the new automated and rapid microlatex D-dimer assay, STA Liatest D-Di, on the STA-R analyzer and to compare it with established D-dimer assays.

METHODS

D-dimer testing has been performed in 103 consecutive outpatients with suspected deep venous thrombosis (DVT). Diagnosis of DVT was established by contrast venography or color-coded duplex ultrasonography. D-dimers plasma concentrations were measured with the STA Liatest D-Di on the STA-R coagulation analyzer, with a reference ELISA technique (Asserachrom), with an automated quantitative latex-based immunoassay (Tinaquant) and with the VIDAS D-dimer test.

RESULTS

In total, 103 eligible outpatients entered the current study and DVT was detected in 46 patients (44.6%). Two duplicate D-dimer measurement with the STA Liatest D-Di revealed excellent correlation (r(S)=0.996) and almost identical sensitivity (each 98%), specificity (49% and 50%), negative predictive value (NPV; each 97%), positive predictive value (PPV; 61% and 62%) and exclusion rate (27% and 28%), respectively. Comparison of the STA Liatest D-Di with the other D-dimer tests revealed highly significant correlations (r(S)=0.951-0.979), highly comparable regression and excellent agreement in clinical interpretation of the test results (kappa coefficients 0.812-0.856). Moreover, sensitivity, specificity, NPV, PPV and exclusion rate at a cut-off level of 500 ng/ml were in the same range for the STA Liatest D-Di when compared with the other D-dimer tests.

CONCLUSION

The Liatest D-Di performed on the coagulation analyzer STA-R compares favorable with the VIDAS, Tinaquant and Asserachrom D-dimer tests and is suitable for the safe exclusion of DVT in symptomatic outpatients. The test can be included in an algorithm for DVT diagnosis including other diagnostic tools.

A detailed analysis of equivocal duplex findings in patients with suspected deep venous thrombosis

OBJECTIVE

To analyze equivocal duplex findings in patients with clinically suspected deep venous thrombosis and thus to increase the diagnostic utility of color duplex sonography in this category of patients.

METHODS

Phlebography was requested in a series of 102 consecutive patients with inconclusive duplex findings. These patients were, according to the duplex findings only, subdivided into having low, intermediate, and high probability of deep venous thrombosis.

RESULTS

Phlebographywas attempted in 71 cases and successfully performed in 49. The remaining 53 patients were prospectively followed clinically for 6 months. Phlebography showed deep venous thrombosis in 1 of 63 patients in the group with low probability, 3 of 31 in the intermediate group, and all of the 8 patients with high probability. Twenty-two (31%) of the 71 attempted phlebographic examinations were nondiagnostic. None of the patients in the follow-up group had any thromboembolic complications.

CONCLUSIONS

Even if a duplex examination is equivocal, it is still possible to extract clinically useful information by categorizing the duplex results into subgroups with low, intermediate, and high probability of deep venous thrombosis. This can have implications for the diagnostic or therapeutic handling of these patients and thus can increase the utility of sonography in patients with inconclusive duplex findings.

Rapid D-dimer testing and pre-test clinical probability in the exclusion of deep venous thrombosis in symptomatic outpatients

We assessed the performance of three rapid D-dimer tests (Auto Dimertest, VIDAS and Tinaquant) in combination with a pretest clinical probability model for deep venous thrombosis (DVT) in 106 consecutive outpatients with suspected DVT. Contrast venography or colour-coded duplex ultrasonography demonstrated the presence of DVT in 47 patients (14 distal DVT and 33 proximal DVT). First, we assessed the accuracy indices for different cut-off levels of the rapid D-dimer tests. Sensitivity was found to be 97.9-100%, negative predictive value (NPV) was 96.3-100%, and the exclusion rate was 24.5-31.1%. Next, the patients were grouped according to the pre-test clinical probability model in categories with low, moderate or high probability. In patients with a low pre-test probability, DVT would have been directly ruled out and the patients would not have undergone further investigations. In patients with a moderate probability, D-dimer testing and, in the case of a positive result, objective testing would have been performed and, in the case of a negative result, they would have been ruled out of having DVT. Patients with high probability would directly have undergone objective tests for DVT. The combination with the pre-test clinical probability model improved the exclusion rate (43.5-44.6%), whereas sensitivity (97.5-100%) and NPV (97.6-100%) remained roughly unchanged. The combination of rapid D-dimer tests with a pre-test clinical probability model may help to reduce unnecessary work-up in patients with suspected DVT.

Ruling out acute deep vein thrombosis by ELISA plasma D-dimer assay versus ultrasound in inpatients more than 70 years old

In geriatric care, deep-vein thrombosis (DVT) is mostly diagnosed by noninvasive techniques. The objectives of this prospective study were: (1) to evaluate the power of ELISA plasma D-dimer assay versus ultrasound (US) in ruling out acute DVT of the lower limbs in symptomatic geriatric inpatients, and (2) to determine the most effective D-dimer cutoff value over the age of 70 years. Over a 10-month period, inpatients with suspected lower limb DVT simultaneously underwent US examination and ELISA plasma D-dimer assay. Noninclusion criteria were comorbid conditions able to modify the D-dimer level. Data were processed by receiver operating characteristic (ROC) curve analysis. In total, 150 patients (125 women, 25 men), average age 86.3 years (range 70-101) were included. A diagnosis of lower limb DVT was established in 53 patients (35.3%). With a 500 ng/mL D-dimer cutoff conventional value, DVT was ruled out in only five patients (3.3%), whereas a 750 ng/mL value ruled out DVT in 19 patients (12.7%) with a sensitivity of 98.1%, and a negative predictive value of 95.0%. The only false negative corresponded to a patient with a 15-mm thrombus in the distal calf. In inpatients above 70, an ELISA plasma D-dimer value smaller than 750 ng/mL is a rapid reliable noninvasive means to rule out lower limb DVT, if color flow Doppler ultrasound is not available on site.

Non-invasive diagnosis of venous thromboembolism in outpatients

BACKGROUND

We designed a simple and integrated diagnostic algorithm for acute venous thromboembolism based on clinical probability assessment of deep-vein thrombosis (DVT) or pulmonary embolism (PE), plasma D-dimer measurement, lower-limb venous compression ultrasonography, and lung scan to reduce the need for phlebography and pulmonary angiography.

METHODS

918 consecutive patients presenting at the emergency ward of the Geneva University Hospital, Geneva, Switzerland, and Hôpital Saint-Luc, Montreal, Canada, with clinically suspected venous thromboembolism were entered into a sequential diagnostic protocol. Patients in whom venous thromboembolism was deemed absent were not given anticoagulants and were followed up for 3 months.

FINDINGS

A normal D-dimer concentration (<500 microg/L by a rapid ELISA) ruled out venous thromboembolism in 286 (31%) members of the study cohort, whereas DVT by ultrasonography established the diagnosis in 157 (17%). Lung scan was diagnostic in 80 (9%) of the remaining patients. Venous thromboembolism was also deemed absent in patients with low to intermediate clinical probability of DVT and a normal venous ultrasonography (236 [26%] patients), and in patients with a low clinical probability of PE and a non-diagnostic result on lung scan (107 [12%] patients). Pulmonary angiography and phlebography were done in only 50 (5%) and 2 (<1%) of the patients, respectively. Hence, a non-invasive diagnosis was possible in 866 (94%) members of the entire cohort. The 3-month thromboembolic risk in patients not given anticoagulants, based on the results of the diagnostic protocol, was 1.8% (95% CI 0.9-3.1).

INTERPRETATION

A diagnostic strategy combining clinical assessment, D-dimer, ultrasonography, and lung scan gave a non-invasive diagnosis in the vast majority of outpatients with suspected venous thromboembolism, and appeared to be safe.

Laboratory diagnosis of venous thromboembolism

Venous thromboembolism is a common medical condition in both out-patients and in-patients. Despite the development of non-invasive tests, the diagnosis of deep vein thrombosis and pulmonary embolism remains a clinical challenge. In an effort to improve diagnostic accuracy and to reduce the necessity of serial testing, laboratory markers of thrombin generation and fibrinolysis have been investigated as first-line screening tests. Although the majority of markers are elevated in acute thrombosis, D-dimer, a specific derivative of cross-linked fibrin, appears to have the most potential clinical utility. Accuracy studies and preliminary management trials suggest that rapid D-dimer enzyme-linked immunosorbent assays and the whole blood agglutination assay, SimpliRED D-dimer (Agen Biomedical, Brisbane, Australia), have strong potential as exclusionary tests in patients with suspected venous thrombosis.

[Role of D-dimers in the diagnosis of thromboembolic disease]

The presence of D-dimers in the bloodstream is secondary to fibrin formation and lysis. Because fibrin is the main component of a thrombus, deep vein thrombosis and/or pulmonary embolism may be excluded with a predictive value of more than 95%, provided D-dimer plasma concentration is below a critical, assay-dependent cutoff. The D-dimer test is thus an ideal screening step in outpatients clinically suspected of venous thromboembolism. Only ELISA tests have been validated in clinical practice at present time for this indication, sensitivity of latex assays being insufficient.