D-dimer concentration increases with age reducing the clinical value of the D-dimer assay in the elderly

• Published in: Internal medicine journal 2007-09, Vol.37 (9), p.607-613
• Main Authors: Harper, P. L, Theakston, E., Ahmed, J., Ockelford, P.
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Aging - blood; Biomarkers - blood; Clinical Chemistry Tests - standards; Cohort Studies; D-dimer; Dimerization; elderly; Female; Fibrin Fibrinogen Degradation Products - metabolism; Humans; Laboratories, Hospital - standards; Male; Middle Aged; pulmonary embolus; Retrospective Studies; Sensitivity and Specificity; Thromboembolism - blood; Thromboembolism - diagnosis; venous thrombosis; Venous Thrombosis - blood; Venous Thrombosis - diagnosis
• ISSN: 1444-0903; 1445-5994
• DOI: 10.1111/j.1445-5994.2007.01388.x

Background: The D‐dimer assay is used as an exclusion test in the assessment of suspected venous thromboembolic disease; patients with a negative result have a low probability of thrombosis. We reviewed the D‐dimer results from a hospital and community laboratory using the vidas D‐dimer test to assess the influence of age on the D‐dimer assay. Methods: D‐dimer results from 6631 unselected patients aged more than 16 years were analysed in four age groups and it was shown that the median D‐dimer concentration increased with age (16–40 years, 294 ng/mL; 40–60 years, 387 ng/mL; 60–80 years; 854 ng/mL; >80 years, 1397 ng/mL). To test the effect of age on the assay specificity, a cohort of 1897 patients with suspected venous thromboembolic disease was analysed separately. Patients with a negative D‐dimer were discharged without further investigation. Patients with a positive result and a clinical suspicion of thrombosis underwent further investigation. One hundred and sixty‐five deep vein thrombosis or pulmonary embolus cases were identified. Results: The assay specificity decreased with age from 70% in patients less than 40 years to below 5% in patients more than 80 years. Receiver operator curves were prepared for each age group and the effect of altering the threshold value was analysed. In patients 60–80 years old a threshold value of 1000 ng/mL increased assay specificity to 55% without loss of assay sensitivity. Conclusion: The vidas D‐dimer assay with a threshold value of 500 ng/mL has little clinical value as an exclusion test in patients more than 80 years old. The assay specificity is poor (26%) in patients aged 60–80 years but could be improved by increasing the threshold value to 1000 ng/mL. We believe that this should be tested in a prospective trial.