The Value of D-Dimer in Evaluating Patients with Suspected Deep Venous Thrombosis in a Predominantly African-American Patient Population.
Layla Alizadeh, Denise M Bellows, Lekidelu Taddesse-Heath. Howard University Hospital, Washington, DC; University of Maryland, College Park
Background: The D-Dimer assay is used as a screening test in patients with clinically suspected deep vein thrombosis (DVT). The utility of the exam is its high sensitivity (98%) and negative predictive value (95%). Patients with D-Dimer values between 0.0-0.5 mcg/ml generally do not require further workup for suspected DVT. African-American patients suffer from a higher incidence of DVT than Caucasians and other racial groups. The purpose of this study is to establish the value of the D-Dimer screening test in evaluating patients with suspected DVT in a predominantly African-American patient population.
Design: Between September 1st, 2009 and November 30th, 2009, 606 consecutive STA-Liatest D-Dimer assays were performed on 572 unique patients. Medical records of these patients were reviewed for clinical history. Only patients with high clinical suspicion and confirmatory Doppler ultrasound were included in the study. Patients without Doppler ultrasound, without clinical suspicion, or having D-Dimer tests performed to rule-out DIC were excluded. The final sample of 195 patients was further divided based on D-Dimer values. D-Dimer values between 0.0 and 0.5 mcg/ml were classified as normal; D-Dimer values above 0.5 mcg/ml were considered elevated.
Results: A total of 180 of 195 (92%) patients were African-American. Of 15 patients with confirmed DVT by Doppler ultrasound. D-Dimer ranged from 0.22 to 25.73mcg/ml. Of the 163 patients with elevated D-Dimer values, 11 had confirmed DVT. Hence, the D-Dimer sensitivity for DVT in this population was 73.3% (11 with elevated D-Dimer out of 15 with proven DVT). The negative predictive value (NPV) of the D-Dimer assay in this study was 87.5% (i.e. 4 confirmed DVT had normal D-Dimer values). A chi-square goodness of fit test comparing sensitivity in the literature to sensitivity in this study found a statistical significance difference in sensitivity (x2= 6.27, p<0.05) without significant difference in NPV (x2 = 6.27). The D-Dimer test in our patient population shows a statistically significant difference in sensitivity (p<0.01) for detection of DVT when compared to the published data (98%). Our study also shows a lower negative predictive value of the D-Dimer test in the evaluation of those patients with suspected DVT (87.5% vs 95%) which is not statistically significant.
Conclusions: Our study highlights the markedly lower sensitivity of D-Dimer in screening African-American patients with suspected deep vein thrombosis.
Tuesday, March 1, 2011 1:00 PM
Poster Session IV # 178, Tuesday Afternoon