The assay picked up all cases but also produced many false-positive results.
No tests for diagnosing deep venous thrombosis (DVT) in pregnancy are perfect. Researchers prospectively evaluated the diagnostic accuracy of a red blood cell agglutination D-dimer assay (SimpliRED) in 149 consecutive pregnant women with suspected DVT at five referral centers in Canada. All women underwent single or serial compression ultrasonography and were followed for at least 3 months. DVT was diagnosed in 13 women (12 by ultrasonography; 1 developed pulmonary embolism at 2 months).
One woman had equivocal D-dimer results and was excluded. The D-dimer assay was positive in 67 women. Of the 13 women with DVT, all had positive D-dimer test results (sensitivity, 100%). Therefore, all of the 81 women with negative test results did not have DVT (negative predictive value, 100%). But of 135 women without DVT, 54 had false positive results (60% specificity). Specificity was lowest in the third trimester.
Comment: Few women had DVT in this study. The SimpliRED assay requires visual interpretation and must therefore be performed by experienced laboratory personnel. This study’s results do not apply to other D-dimer assays. Nonetheless, D-dimer testing may have some clinical utility in excluding DVT in pregnant women.
— Richard Saitz, MD, MPH, FACP, FASAM
Published in Journal Watch General Medicine August 21, 2007
Chan W-S et al. A red blood cell agglutination D-dimer test to exclude deep venous thrombosis in pregnancy. Ann Intern Med 2007 Aug 7; 147:165-70.