Thrombopoietin external quality assessment – laboratory results and method precision

Introduction The aim of the study was to investigate the measurement quality of medical laboratories with regard to thrombopoietin (TPO) determinations within the framework of an external quality assessment (EQA) scheme. Since the results of the past EQA runs since the introduction of the TPO EQA in 2017 were not entirely conclusive, due to the consistently low number of participants, a much more detailed investigation was carried out in this study design with a higher number of samples. Method A total of five laboratories took part in the study and were asked to generate two serum samples, of which one had to show a low thrombocyte concentration. The total of 12 different samples were distributed to the participating laboratories and measured using enzyme-linked immunosorbent assay (ELISA) at least in duplicates. The participating laboratories reported back the respective optical density values at 450 nm (OD 450 ) for the samples as well as the assay standards and blanks. Results The results show variability in the measurements between participating laboratories. The average deviation from the mean value of the determined TPO concentrations in the samples is 25.9±19.6%. The average intra-assay variation (Coefficient of Variation) based on the results of the multiple measurements of the optical density values is 5.6±4.8%. The average limit of blank, representing the maximum background signals, was at an OD 450 of 0.146±0.051 with an average OD 450 of 0.179±0.054 for the assay calibrator with the lowest concentration of 31.3 pg/mL. Two laboratories were in some cases unable to detect OD 450 -signals for samples exceeding the TPO levels of the highest calibrator, at 2000 pg/mL. Conclusion This study highlights the importance of EQA, particularly in relation to the harmonization of TPO measurements. The observed variations underscore the need for continuous objective assessments of measurement quality to ensure reliable TPO test results and patient safety. Publication History Article published online: 17 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany