Background: The erythrocyte sedimentation rate (ESR) test is one of the most frequently performed in clinical laboratories. In addition to traditional ESR methods such as the Westergren and Wintrobe methods, these methods have been diversified in recent years. We investigated the current status of ESR methods in Korea and the distribution of ESR results according to the methods based on the external quality assessment (EQA) data of the Korean Association of External Quality Assessment Service.
Methods: Data from the ESR EQA, conducted twice a year from 2018 to 2021, were collected. We investigated the ESR methods, equipment usage status, and ESR results according to the methods. We also analyzed trends in proficiency test results by year.
Results: The alternate method was the most frequently used ESR method in Korea (56.0%). The distribution of interlaboratory coefficients of variation (CVs) was 21.4%±14.3% (mean±standard deviation) for the Wintrobe method, 33.4%±12.8% for the Westergren method, and 22.8%±19.7% for the modified Westergren method, with no statistically significant difference between the three methods. The interlaboratory CVs of the alternate method were significantly lower than those of all other methods (6.2%±2.2%, P<0.001). The interlaboratory CVs showed a tendency to gradually decrease by year for all methods.
Conclusions: Automated ESR methods are used in most laboratories in Korea. The interlaboratory CVs were lowest for the alternate method and tended to decrease as EQA was implemented. The ESR EQA is expected to improve the quality of the ESR.

Keywords: Erythrocyte sedimentation rate, External quality assessment, Westergren method, Wintrobe method, Alternate erythrocyte sedimentation rate method