An age-adapted approach for the use of D-dimers in the exclusion of deep venous thrombosis

Abstract

A normal D-dimer (DD) concentration for the exclusion of deep venous thrombosis (DVT) has a low specificity in older patients and compression ultrasonography is often required. Three D-dimer assays, STA Liatest, Tina-quant, and Innovance, are evaluated in symptomatic outpatients suspected for DVT with emphasis on its performance in older patients by using different cut-off levels. This study includes 466 outpatients suspected for having DVT. The diagnostic accuracy, measured as sensitivity and area under the curve of the receiver operation characteristic curve is good for all DD assays. The specificity of the DD assays combined with a low pretest probability varies from 42.6 to 51.5%. The specificity of the three DD assays in patients ‡60 years varies, however, between 24.6 and 40.9%. Several cut-off values in different age-subgroups are studied. For patients <60 years, the most accurate cut-off value is 500 lg/L for all DD assays. For patients ‡60 years, a threshold of 750 lg/L has the best results with NPV of 100% for all assays and specificity of 48.5% (STA Liatest), 60.6% (Tina-quant), and 49.2% (Innovance), respectively. For the three assays, the number needed to test (NNT) decreases in both subgroups of patients compared to the standard algorithm. Introduction The use of the D-dimer (DD) assay as screening test for exclusion of venous thromboembolism (VTE) is well documented Although this strategy is widely accepted, there are some serious limitations in the use of DD assays. There is an assay-dependent variability in specificity for conditions such as thrombosis or disseminated intravascular coagulation A recent study reports that the clinical usefulness of DD measurement decreases with age The objective of this study is to evaluate the use of ageadapted cut-off values for three DD assays in symptomatic outpatients suspected for having deep venous thrombosis (DVT)