Validation of an automated immunoturbidimetric assay for measurement of plasma D-dimer

The performance characteristics and diagnostic accuracy of a new rapid automated quantitative immunoturbidimetric D-dimer assay, Auto-Dimer (Biopool, Umeå, Sweden) were evaluated in a population of 135 outpatients with suspected deep-vein thrombosis of a lower limb. Enzyme-linked immunosorbent assay was used as the reference method. The Auto-Dimer assay showed good reproducibility. The correlation between Auto-Dimer and enzyme-linked immunosorbent assay was high (r = 0.91, p < 0.05) and agreement in classifying patients above or below the cut-off was good (kappa coefficient 0.74, 95% CI 0.62-0.86). At a cut-off of 340 microg/l the sensitivity and specificity of Auto-Dimer were high (100% and 61%, respectively). These data show that Auto-Dimer is a reliable screening test for exclusion of deep-vein thrombosis. The assay could be included in prospective patient management studies in order to obtain further information on its clinical usefulness.