Adapting the D-dimer cutoff for thrombosis detection in elderly outpatients

D-dimer measurement is an important step in diagnostic strategies for venous thromboembolism. It allows the safe ruling out of the diagnosis with no need for imaging tests in approximately 30% of outpatients. However, the usefulness of d-dimer is limited in elderly patients; the likelihood of a negative d-dimer strongly decreases with age, making physicians reluctant to order the test. Several attempts to improve the performance of D-dimer in elderly patients have been pursued. Recently, an age-adjusted cutoff was derived; the optimal cutoff value (in µg/l) appears to be equal to the patient's age (in years) multiplied by ten in patients over 50 years of age with a low pretest clinical risk of venous thromboembolism. This age-adjusted cutoff value has been extensively and externally validated in retrospective studies that included mostly outpatients with suspected deep vein thrombosis or pulmonary embolism and used various quantitative D-dimer assays. All available studies confirmed the increased usefulness and similar safety of the age-adjusted cutoff compared with the conventional cutoff, the most important benefit being obtained in elderly patients. However, before any recommendation for clinical practice can be made, a prospective diagnostic management outcome study is lacking, in which all low clinical risk patients with D-dimer levels below their age-adjusted cutoff would be left untreated with no further diagnostic testing.