Age‐adjusted D‐dimer cut‐off levels to rule out venous thromboembolism in patients with non‐high pre‐test probability: Clinical performance and cost‐effectiveness analysis

Summary

Background

As aging was found to be associated with increased D‐dimer levels, the question arose whether D‐dimer measurement was useful in the diagnostic strategy of venous thromboembolism (VTE) in elderly patients.

Aim of the study

To compare retrospectively the performance of six diagnostic strategies based on the three‐level Wells scores and various cut‐off levels for D‐dimer, evaluated using the HemosIL D‐Dimer HS 500 assay, in a derivation cohort of 644 outpatients with non‐high pretest probability (PTP) of VTE. The clinical usefulness of the best‐performing strategy was then confirmed in a multicenter validation study involving 1255 consecutive outpatients with non‐high PTP.

Results

The diagnostic strategy based on the age‐adjusted cut‐off level calculated by multiplying the patient's age by 10 above 50 years was found to perform the best in the derivation study with a better sensitivity‐to‐specificity ratio than the conventional strategy based on the fixed cut‐off level (500 ng/ml), a higher specificity and a negative predictive value (NPV) above 99%. Such an increase in test specificity was confirmed in the validation cohort, with the NPV remaining above 99%. Taking into account the local reimbursement rates of diagnostic tests, using this strategy led to a 6.9% reduction of diagnostic costs for pulmonary embolism and a 5.1% reduction for deep vein thrombosis, as imaging tests would be avoided in a higher percentage of patients.

Conclusion

The diagnostic strategy of VTE based on the age‐adjusted cut‐off level for D‐dimer in patients over 50 years was found to be safe, with NPV above 99%, and cost‐effective.