A-137 Performance Evaluation of an Automatic, Rapid and Non-Westergren Based Method for Erythrocyte Sedimentation Rate Measurement

Abstract

Abstract The erythrocyte sedimentation rate (ESR) is widely used for the assessment of acute or chronic inflammation, especially for rheumatoid diseases. The gold standard for determining ESR is the Westergren method, which measures the distance in millimeters that red blood cells fall in one hour. However, this method needs to be performed manually, which increases the biohazard risk to laboratory personnel, and the results are often influenced by many preanalytical and analytical factors. Several automated ESR analyzers with different methodologies are now available to provide faster results directly from whole blood anticoagulated with K3EDTA. In this study, we evaluated the performance of an automatic ESR analyzer, Alifax TEST1, and compared it with that of another automatic analyzer, Diesse Cube 30 touch, and also the Westergren method. TEST1 extrapolates the ESR values by measuring the kinetics of red cells aggregation in 20 s, while Cube 30 is a modified Westergren method that could obtain the results in 20 min. A total of 75 clinical samples were analyzed for ESR using the three methods. The hematocrit (Hct) and C-reactive protein (CRP) values were also analyzed. The Spearman correlation coefficient between TEST1 and Westergren methods was 0.90 (P < 0.0001) with a mean difference of -5.45; the correlation between Cube 30 and Westergren methods was 0.80 (P < 0.0001) with a mean difference of 10.74; the correlation between TEST1 and Cube 30 was 0.69 (P < 0.0001) with a mean difference of -15.9. The precision values (CV %) of TEST1 in low-, medium- and high-level controls were 2.71%, 1.21% and 1.05% for inter-assay, and 3.70%, 1.66% and 0.86% for intra-assay. The normal range of TEST1 was also established by analyzing ESR values of 125 healthy individuals where it is 0–15 mm/hr for men ≤50years old, 0–20 mm/hr for men > 50 years old and for women ≤50 years old, and 0–30 mm/hr for women > 50years old. The ESR values obtained from the three methods all significantly correlated with plasma CRP levels. However, the ESR values from Cube 30 and Westergren methods negatively correlated with Hct values, while that from TEST1 did not. The present study demonstrates that 1) TEST1 has a better correlation and a lower difference to the Westergren method compared to Cube 30, suggesting that TEST1, the automatic, rapid and non-Westergren based method is an effective assay for clinical practice; 2) the Westergren based methods are more easily influenced by Hct; 3) the large mean difference between TEST1 and Cube 30 highlights a need for harmonization of the ESR values obtained from different automatic analyzers, especially when it is applied to monitor the disease activity score (DAS28) in rheumatoid arthritis patients.