Automated measurement of the erythrocyte sedimentation rate: method validation and comparison

Background: Development of automated analyzers for erythrocyte sedimentation rate (ESR) has imposed the need for extensive validation prior to their implementation in routine practice, to ensure comparability with the reference Westergren method. The aim of our study was to perform the analytical validation of two automated ESR analyzers, the Ves-Matic Cube 200 and the TEST1. Methods: Validation was performed according to the recent International Council for Standardization in Hematology recommendations and included determination of intrarun and inter-run precision, assessment of sample carryover, hemolysis interference, sensitivity to fibrinogen, method comparison with the gold standard Westergren method and stability test. Results: The highest intrarun imprecision was obtained for the low ESR range (33.5% for Ves-Matic Cube; 37.3% for TEST1) while inter-run coefficients of variation on three levels were much better for the TEST1 (0%, 2% and 1.2%) compared to the Ves-Matic Cube 200 on two levels (24.9% and 5.8%). Both Ves-Matic Cube 200 and TEST1 showed no statistically significant difference when compared with Westergren. Bland-Altman analysis yielded overall insignificant mean biases for all comparisons, but a wider dispersion of results and 95% limits of agreement for comparisons including the Ves-Matic Cube 200. Carryover was considered insignificant, while hemolysis had a negative effect on all assessed ESR methods. The highest sensitivity to fibrinogen was observed for the Ves-Matic Cube 200, followed by Westergren and the least sensitive was the TEST1. Conclusions: The obtained results proved the analytical validity of the TEST1 and the Ves-Matic Cube 200, and high comparability with the gold standard Westergren method, showing obvious improvements in standardization of ESR methods.