## Abstract

**Background:** For automation it is important to know the effect of analyzing fresh samples after a single rather than after two centrifugations, and to determine test stability.

**Methods:** This study compared silica clotting times (SCT) and dilute Russel’s viper venom tests (dRVVT) after one and two centrifugations in 50 fresh plasma samples. Then it compared test results within 4 h to those after 6–8 h of blood drawing in 40 samples. Means, minimums, maximums and quartiles of the paired screen were compared, test ratios were confirmed and correlations, linear regressions and Bland-Altman statistics were calculated.

**Results:** The distributions of test results were nearly identical, regardless of the number of centrifugations or timing of the analysis. The first centrifugation explained 97.7% and 94.8% of the variance of tests results after the second centrifugation for the SCT and dRVVT, respectively. The test results after 6–8 h explained 98.3% and 96.3% of the variance of the SCT-ratios and dRVVT-ratios, respectively, tested within 4 h. Inter-day coefficients of correlation of ratio comparisons were similar to those of the controls values.

**Conclusions:** Testing of fresh samples after a single centrifugation might replace batch testing of frozen samples after double centrifugation, providing timelier reporting of results and resulting in savings of technician time.

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