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

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 We compared the iSED with the predicate modified Westergren method (StaRRsed, Mechatronics, Zwaag, the Netherlands) measured at 60 minutes. Analysis was performed on K 2 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.