Evaluation of Control Materials for Erythrocyte Sedimentation Rate Measurement by Using the Modified Westergren Method

Evaluation of Control Materials for Erythrocyte Sedimentation Rate Measurement

Abstract

         Erythrocyte Sedimentation Rate (ESR) measurement is a widely used test to assess inflammation or response in the acute phase. There is only one service unit available in Thailand which is insufficient, thus, proficiency testing (PT) materials need to be developed to supply to establish more test sites. This study aimed to evaluate the control materials prepared for ESR testing with the modified Westergren method. The materials consisted of glutaraldehyde-preserved red blood cells and plasma evaluated for homogeneity and stability according to the ISO 13528:2022 standards. Following these, the material samples were sent to 15 medical technology laboratories for evaluation over 2 rounds. Each round consisted of 3 samples: 2 samples were at normal levels and 1 sample at abnormal levels. The Z-score value was used to assess the results, with a value of | Z | < 2 considered passing. The study results showed that the ESR control materials at both levels in both rounds of preparation were homogeneous and stable. The evaluation of ESR control material samples by 15 medical technology laboratories found consistent results. For the normal level, 2 samples had | Z | < 2 in 14 laboratories (93.3%), and for the abnormal level, 1 sample had | Z | < 2 in all 15 laboratories (100%). This study demonstrated that most laboratories provide accurate test results. However, increasing the number of laboratories in the evaluation would further enhance confidence in these control materials. Further development of these control materials will lead to the self-prepared proficiency testing materials for ESR proficiency testing of the modified Westergren method.