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

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Abstract 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.
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Keywords: D-dimer; elderly; pulmonary embolus; venous thrombosis

Document Type: Research Article

Affiliations: 1: Diagnostic Medlab, Auckland 2: Department of Medicine, Auckland City Hospital, Auckland, New Zealand

Publication date: 01 September 2007

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