Improving D-dimer Positive Predictive Value for Outpatients with Suspected Deep Vein Thrombosis

Improving D-dimer Positive Predictive Value for Outpatients with Suspected Deep Vein Thrombosis


Craig M Nelson, PhD, CLS; Geary S Wright, BA, MLT; Tom R Silbaugh, CPT; Louis J Cota, CLS

Winter 2009 - Volume 13 Number 1


Context: Sensitive D-dimer assays have been developed to exclude the diagnosis of deep vein thrombosis (DVT) and have exhibited great success when used in conjunction with a diagnostic algorithm, including pretest probability scoring and a compression ultrasound (CUS). Improving specificity of D-dimer assays would significantly improve the utility of CUSs.

Objective: Our objective was to evaluate the ability of a new D-dimer assay to improve specificity, positive predictive ability, and Bayesian probability when compared with an assay previously used in our laboratory.

Methods: We retrospectively reviewed 1015 continuous patients with suspected DVT. All patients were clinically evaluated in our laboratory with a D-dimer assay: 503 were clinically evaluated with a bioMérieux D-dimer test system and 512 were evaluated with a Trinity Biotech D-dimer test system. Outcomes were assessed statistically using sensitivity, negative predictive value, Bayesian negative probability, specificity, positive predictive value, and Bayesian positive probability.

Results: The data for our study showed that with the Trinity Biotech D-dimer assay, specificity increased from 41.3% to 66.9%, positive predictive value increased 2.3 times from 8.8% to 20.0%, and the probability of DVT after positive results on a D-dimer test increased from 25% to 38% when compared with the bioMérieux D-dimer test system. In addition to the improved parameters for clinical performance, a significant number of unneeded CUSs were saved. The number of false positive D-dimer assays significantly decreased and positive predictive ability improved when the Trinity Biotech test system was used in our laboratory.

The Permanente Journal

Sponsored by the eight Permanente Medical Groups, The Permanente Journal advances knowledge in scientific research, clinical medicine, and innovative health care delivery.

Reprint Permissions

The Permanente Journal welcomes requests for reprints and reproduction. Use of any and all material published in The Permanente Journal is copyrighted and protected.

The Permanente Press

The Permanente Press publishes The Permanente Journal and books related to healthcare. Journal subscriptions are entered for the calendar year. Advance payment in US dollars is required.

ISSN 1552-5775 Copyright © 2018

The Permanente Press. All Rights Reserved.