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RESEARCH PRODUCT

Benefit of using an age-adjusted D-dimer cut-off

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Introduction: The association between a low-moderate pretest clinical probability and a negative D-dimer (DD) value is able to exclude the possibility of pulmonary embolism (PE). The value of DD seems to increase with age, reducing its specificity. Therefore, we intend to evaluate the usefulness of an age-adjusted cut-off value for age above 50 years, applying the formula suggested by Douma (age*10) set to our laboratory method (age*5) (1) . Patients and Methods: Observational, retrospective study from January to December 2011. DD test were performed to 1515 patients attended in the emergency room of our hospital according to the clinical suspicion made by the doctor who evaluated them. The correlation between DD and age was studied using the Pearson correlation test. Sensitivity, specificity, positive predictive value and negative predictive value were calculated applying the determinate cut-off and the age-adjusted cut-off following the formula proposed. Results: Mean age was 72 years; 50% men. EP was diagnosed in 55 patients, all of them with positive DD test using both cut-offs. Using the cut-off established by our laboratory of 250 mg/dL, have a negative DD test 317 patients (20.92%) [Se=100%;Sp=21.72%;PPV=4.59%;NPV=100%]. Using the Douma formula the patients with negative DD test amounts to 493 (32.54%) [Se=100%;Sp=33.76%;PPV=5.38%;NPV=100%]. After a year of follow-up none showed a thrombotic event. Among patients with unknown cause of DD increasing, it correlates positively with age (r=0.19;p Conclusions: Using an age-adjusted cut-off improve specificity of the test and thus avoid unnecessary diagnostic test. Although weak, a positive correlation between DD and age is shown. (1) Douma RA. BMJ2010;340:c1475 Project support by FNCV.