Abstract
IntroductionAutomated erythrocyte sedimentation rate (ESR) analysers are based on different methodology than Westergren method. It is questionable whether ESR values obtained from those analysers are comparable with determined values with Westergren method. The aim was verification of the precision, method comparison and accuracy of automated ESR analysers: Roller 20PN (Alifax S.p.A., Polverara, Italy) and iSED (Alcor Scientific, Smithfield, USA).Materials and methodsBlood samples (N = 752 for Roller 20PN and N = 213 for iSED) were sampled into K2EDTA (Kima, Italy) tubes for automated and 3.8% Na-citrate tubes (Kima, Italy) for Westergren method. The data was divided into three groups according to the ESR values obtained with the Westergren method: Group Low (L) (ESR ≤ 20 mm), Group Medium (M) (ESR 21-60 mm), and Group High (H) (ESR ≥ 61 mm). Method agreement was assessed by Bland-Altman analysis and Passing-Bablok regression.ResultsAnalyser iSED has shown better comparability with Westergren method (bias 0.0 (95%Cl -1.4 to 1.5) range than Roller 20 PN (bias = - 6.4 (95%Cl - 7.1 to -5.7) in the whole measuring. For Roller 20 PN, Passing-Bablok regression has shown constant and proportional difference for Groups L and M, and for iSED only for Group H. Roller 20 PN had lower sensitivity (0.51 (95%Cl: 0.45-0.57) than iSED (0.72 (95%Cl: 0.59-0.80) while they had comparable specificity (> 0.90) and accuracy (≥ 0.80) in comparison with the Westergren method.ConclusionBoth analysers are not comparable with the Westergren method and should not be used interchangeably.
Highlights
Automated erythrocyte sedimentation rate (ESR) analysers are based on different methodology than Westergren method
The wider acceptable range defined by the manufacturer for Seditrol quality control sample Level 1 for analyser iSED may be the reason for higher CV%
14 of 15 measurements were within the range of 8-13 mm, and only one measurement was 4 mm which was still within the defined range declared by the manufacturer (2-16 mm) but significantly alters CV%
Summary
Automated erythrocyte sedimentation rate (ESR) analysers are based on different methodology than Westergren method. It is questionable whether ESR values obtained from those analysers are comparable with determined values with Westergren method. Erythrocyte sedimentation rate (ESR) is a widely used assay which is still among the top 25 most common laboratory tests [1]. Many physiological and pathophysiological causes can increase the ESR values which make this test nonspecific, e.g., in pregnancy, for women who have menstruation, at an older age, arthritis and inflammatory bowel disease [2]. Westergren method uses whole blood sample that is diluted with a liquid citrate anticoagulant (4:1) and the value of ESR is determined after one hour in a vertically placed tube.
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