Erythrocyte sedimentation rate measurements using MIX-RATE® X20 and VISION A automated analyzers: Method validation and comparison study.

BACKGROUND

The Westergren method for erythrocyte sedimentation rate (ESR) measurement has a few drawbacks such as being a time-consuming process, poses a risk of biohazard exposure and requires high sample volume. Recent alternative methods and analyzers were developed to overcome those limitations. In this study, we validated two automated ESR analyzers, MIX-RATE® X20 and VISION A, and assessed their analytical performance against the Westergren method.

METHODS

The analyzers were validated for inter-run and intra-run precision. Hemolysis interference and sensitivity to fibrinogen were also analysed. Analytical performance was performed using 177 patient samples spanning low (<40 mm/h), medium (40-80 mm/h), and high (>80 mm/h) ESR ranges. Method agreement and bias against the Westergren method were calculated.

RESULTS

The highest intra-run imprecision was seen in the low ESR range for both analyzers. They showed very high agreement with the Westergren method assessed by Spearmen rank correlation coefficient analysis, r = 1.000, p < .0001 for both analyzers. Bland-Altman analysis yielded overall insignificant mean biases for all comparisons. However, systematic positive and negative bias were observed at medium and high ESR levels analysed by MIX-RATE® X20 while negative bias was evidenced in the high ESR level measured by VISION A.

CONCLUSIONS

Overall, results from both automated ESR analyzers showed comparable analytical performance with the Westergren method especially for low ESR levels. However, both positive and negative systematic bias were documented in the high levels. Thus, for clinical use, it must be assessed whether these biases could affect the cut-off for significant clinical values.