Factors associated with positive D-dimer results in patients evaluated for pulmonary embolism.
OBJECTIVE
Available D-dimer assays have low specificity and may increase radiographic testing for pulmonary embolism (PE). To help clinicians better target testing, this study sought to quantify the effect of risk factors for a positive quantitative D-dimer in patients evaluated for PE.


METHODS
This was a prospective, multicenter, observational study. Emergency department (ED) patients evaluated for PE with a quantitative D-dimer were eligible for inclusion. The main outcome of interest was a positive D-dimer. Odds ratio (ORs) and 95% confidence intervals (CIs) were determined by multivariable logistic regression. Adjusted estimates of relative risk were also calculated.


RESULTS
A total of 4,346 patients had D-dimer testing, of whom 2,930 (67%) were women. A total of 2,500 (57%) were white, 1,474 (34%) were black or African American, 238 (6%) were Hispanic, and 144 (3%) were of other race or ethnicity. The mean (+/-SD) age was 48 (+/-17) years. Overall, 1,903 (44%) D-dimers were positive. Model fit was adequate (c-statistic = 0.739, Hosmer and Lemeshow p-value = 0.13). Significant positive predictors of D-dimer positive included female sex; increasing age; black (vs. white) race; cocaine use; general, limb, or neurologic immobility; hemoptysis; hemodialysis; active malignancy; rheumatoid arthritis; lupus; sickle cell disease; prior venous thromboembolism (VTE; not under treatment); pregnancy and postpartum state; and abdominal, chest, orthopedic, or other surgery. Warfarin use was protective. In contrast, several variables known to be associated with PE were not associated with positive D-dimer results: body mass index (BMI), estrogen use, family history of PE, (inactive) malignancy, thrombophilia, trauma within 4 weeks, travel, and prior VTE (under treatment).


CONCLUSIONS
Many factors are associated with a positive D-dimer test. The effect of these factors on the usefulness of the test should be considered prior to ordering a D-dimer.
Kabrhel
Christopher
C
Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. ckabrhel@partners.org
Mark Courtney
D
D
Camargo
Carlos A
CA
Plewa
Michael C
MC
Nordenholz
Kristen E
KE
Moore
Christopher L
CL
Richman
Peter B
PB
Smithline
Howard A
HA
Beam
Daren M
DM
Kline
Jeffrey A
JA
D000328:Adult; D000368:Aged; D004636:Emergency Service, Hospital; D005260:Female; D005338:Fibrin Fibrinogen Degradation Products / Q000032:analysis; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000175:diagnosis* / Q000453:epidemiology; D012307:Risk Factors
D005338:Fibrin Fibrinogen Degradation Products; C036309:fibrin fragment D