In reply. We are most grateful to Dr Siragusa for highlighting the important issue of the potential for false-negative results when plasma D-ds are used as an exclusionary test for VTE in patients already receiving heparin. In the report by Couturaud et al,1 pooled data from 3 studies showed that D-d levels in patients with VTE decreased by 25% after 24 hours of anticoagulant therapy. Although the absolute levels at this stage were 10-fold higher than the reference limit, this still resulted in a small decrease in sensitivity that might be clinically significant. Furthermore, D-d assay may also be less sensitive in patients receiving ongoing oral anticoagulation who have a suspected new episode of VTE: in a retrospective study of 704 outpatients with suspected deep vein thrombosis (DVT), the overall sensitivity of the Minutex assay (Diapharma Group, Inc, West Chester, Ohio) was 99%, falling to 75% in 61 patients receiving oral anticoagulants.2
Kelly J, Hunt BJ. Plasma D-Dimer Test Accuracy Can Be Affected by Heparin Administration—Reply. Arch Intern Med. 2003;163(2):247. doi:10.1001/archinte.163.2.246-a
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