Differences in erythrocyte sedimentation rates using a modified Westergren method and an alternate method

Abstract

INTRODUCTION: Worldwide laboratories have adopted the use of modified or alternate methods for measurement of the erythrocyte sedimentation rate (ESR). The iSED from Alcor Scientific is a novel, alternate ESR method based on photometric aggregometry which offers improved operator safety and reduced analysis time. This study evaluated the diagnostic utility of the iSED in a South African patient population with a range of inflammatory disorders. METHODS: EDTA samples at three ESR measurement ranges (<20, 20-80 and >80 mm/h) in 120 pediatric and adult inpatients and outpatients over a 2-week period. Precision, stability, and carryover were performed in accordance with the revised International Council for Standardisation in Haematology guidelines. RESULTS: The iSED demonstrated acceptable imprecision with minimal carryover (2.86%). The correlation coefficients at the 3 ESR measurement ranges were r = 0.58, r = 0.71, and r = 0.56, respectively. The y-intercepts were -10.74 (CI -29.17 to 7.69), -5.95 (CI -18.60 to 6.69) and 246.05 (CI 591.42-99.31). This indicated a difference of a constant nature with an overall mean difference of 7.99 mm/h (CI 5.87-10.13) (P < 0.001). iSED ESR measurements were stable up to 24 hours when stored at room temperature or at 4-8°C. CONCLUSION: This study demonstrated differences in ESR results, predominantly at extremes of the analytical range, using an alternate method. Careful consideration and performance monitoring of these novel methods are advised.