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.

We compared the iSED with the predicate modified Westergren method (StaRRsed, Mechatronics, Zwaag, the Netherlands) measured at 60 minutes. Analysis was performed on K₂ 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.

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.

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.