The VIDAS D-dimer test for venous thromboembolism: a prospective surveillance study shows maintenance of sensitivity and specificity when used in normal clinical practice

Abstract

Background As a result of a number of clinical management studies, D-dimer (DD) tests such as VIDAS (BioMérieux Australia P/L-Sydney, NSW) have been recommended to reduce venous thromboembolism (VTE) investigations. Surveillance studies for new tests are recommended. We prospectively assessed VIDAS DD in normal practice. Methods Consecutive emergency patients and inpatients (IPs) with DD or VTE investigations were prospectively identified. Investigation results and early chart review including predefined factors reducing specificity were documented. A latex DD was also performed. Patients were followed for at least 3 months for recurrent VTE. Results Four hundred three patients (emergency, 64%; VTE-positive, 12%; 95% followed up) were analyzed. VIDAS sensitivity was 96% (95% confidence interval 86%-99%), specificity 38% (confidence interval, 34%-44%; negative likelihood ratio, 0.11), and emergency specificity 51%. Latex sensitivity was 76%. Cancer, trauma, recent operations, IP status, and advanced age were associated with markedly reduced specificity. Specificity in older emergency patients (>70 years old) and younger IPs (<70) without comorbidities was 20% to 30%, but sensitivity was maintained at 100%. Conclusions VIDAS DD probably maintains adequate sensitivity in normal clinical practice for low- or even intermediate-risk patients. Latex agglutination had poor sensitivity. Specificity is best in younger low-morbidity emergency patients. These findings need validation in larger multicenter surveillance studies.