Development and implementation of the external quality assessment program for erythrocyte sedimentation rate in hematology laboratories in Thailand

Background: The erythrocyte sedimentation rate (ESR) remains the most widely used screening test for monitoring the course of infections, inflammatory diseases, and some types of cancer. Proficiency Testing (PT) programs are unavailable in Thailand for ESR. Objective: This study aimed to develop and initiate the PT program to improve testing quality through evaluation and analysis of the laboratory test results for ESR. Materials and methods: The PT program for ESR was established at the AMS CMU EQA Unit by the ISO/IEC17043:2010 requirements. The unit produced and sent the ESR control materials to participants for laboratory analysis; the test results were returned to the unit. The PT program was carried out in two cycles per year, with two samples in each cycle. The performance of each laboratory was assessed using robust Z score and performance score. Results: ESR control materials presented with satisfactory homogeneity and stability according to ISO 13528: 2015. One hundred and four laboratories were enrolled in the PT program. Of these laboratories, 96 (92.3%) returned their data: 40 (42.7%) used the modified Westergren method, 29 (29.2%), 14 (15.7%), and 13 (12.4%) used Microsed, Mixrate, and other methods, respectively. Satisfactory and questionable performance was obtained in 82/96 (85.4.%) and 8/96 (8.3%), respectively. Unsatisfactory performance was noted at 6/96 (6.3%). The level of excellent performance was achieved by 82 (approx. 85%) of these laboratories. Two main types of errors found from analyzing the received data were (i) specimen processing and (ii) incorrect identification of the analytical method. Conclusion: Our results indicate that the advantage of participation in the PT program for ESR is that the laboratories can monitor and investigate the source of laboratory errors. Therefore, the PT program for ESR testing should become an integral part of the quality assurance system in the laboratory.