Age-adjusted D-dimer for the diagnosis of deep vein thrombosis.

Objective In the diagnosis of deep vein thrombosis, new D-dimer cut-off values were defined by multiplying 10 µg/L × age. The objective of the present study is to define a more specific age-adjusted value, including the pre-test Wells score, without worsening sensitivity. Methods We designed a case-control study in patients attended in the emergency department with clinically suspected deep vein thrombosis. Demographics, Wells score, D-dimer and ultrasound data were collected. In low and intermediate clinical probability cases for deep vein thrombosis, we determined the specificity and sensitivity (false-negative rates) for the following cut-off values of D-dimer: age × 10 µg/L, age × 15 µg/L, age × 20 µg/L, age × 25 µg/L and age × 30 µg/L. The cut-off value with maximum specificity without any false-negative result (sensitivity 100%) was identified. Results We included 138 consecutive patients, 39.9% were men and the mean age was 71.6 years. Deep vein thrombosis was diagnosed in 16.7% of patients and the Wells score was low in 69.6%, intermediate in 21% and high in 9.4% of patients. Applying the conventional cut-off value of 500 µg/L, the specificity was 21.1% with a sensitivity of 100%. Maintaining 100% sensitivity, the highest specificity was reached with a cut-off value for D-dimer equivalent to the age × 25 µg/L in low-risk patients (67.1% specificity) and the age × 10 µg/L (50% specificity) in intermediate-risk patients. Conclusions In patients with low Wells score, the cut-off value can be raised to age × 25 µg/L in order to rule out deep vein thrombosis without jeopardizing safety. In intermediate-risk patients, the D-dimer cut-off value could be raised to age × 10 µg/L as previously suggested.