Normal D-dimer concentration is a common finding in symptomatic outpatients with distal deep vein thrombosis
The D-dimer analysis has been shown to have a high sensitivity and a high negative predictive value for the exclusion of deep vein thrombosis (DVT). However, most D-dimer studies, including recent clinical management studies, are performed without examination of the calf veins and/or performed on patient populations with a predominance of proximal DVT. The purpose of this study was to evaluate the diagnostic performance of the D-dimer test in a population with a suspected high incidence of distal DVT. In the present study, 393 outpatients with clinically suspected symptomatic DVT of the lower extremities were examined with whole-leg duplex ultrasonography. The D-dimer analysis was performed using an automated micro-latex assay (Tina-quant). A total of 137 of 393 patients had a proven DVT, with the majority presenting with distal DVT (59%). Twenty-eight out of 81 patients with distal DVT had a normal D-dimer, compared with two of 56 patients with proximal DVT. The sensitivity for distal DVT was only 65% compared with 96% for proximal DVT; the negative predictive values were 84 and 99%, respectively. In conclusion, the prevalence of distal DVT in a study population seems to have a great impact on the diagnostic performance of the D-dimer analysis. The study results also show that normal D-dimer levels do not exclude distal DVT in outpatients; instead, it can be hypothesized that normal D-dimer levels exclude DVT that require treatment, as indicated by the good outcome in recent management studies.