Correia, Helenadas Neves Pereira da Silva, SusanaMiranda, ArmandinaFaria, AnaWeykamp, CasSiebelder, Carla2026-03-042026-03-042025-10-15http://hdl.handle.net/10400.18/11109Introduction: The determination of glycated hemoglobin (HbA1c) is used in patients with diabetes mellitus as a key to monitoring the long-term blood glucose control (1). The Portuguese National External Quality Assessment Program (PNAEQ), organizes since 2003 the Hemoglobin glycated (HbA1c) program for External Quality Assessment Laboratory and integrated the IFCC EurA1c project in 2017. External Quality Assessment (EQA) is a powerful education tool to monitor quality that, by identifying poor performing laboratories and test systems, can be used as a tool to improve quality (2). Objective: Monitor the analytical performance of HbA1c determination, performed by PNAEQ participants, based on results of their participation in EurA1c project (bias (%) and coefficient of variation (CV%). Methods: From 2017 to 2024, PNAEQ laboratory participants (mean=41), from public and private sectors of ambulatory and hospital care, analysed in first round, two control samples per year, (n=16), with different concentrations (samples below and above 48mmol/mol). The samples sent from EurA1c project were lyophilized hemolysate specimens manufactured from the same pool. Participants HbA1c results, in IFCC units, were evaluated by comparison with target values assessed by EurA1c project. Usually, values were assigned by five laboratories using the IFCC Reference Measurement Procedure. The statistical analysis followed the EurA1c project´s methodology. Outliers- defined as results differing by more than 25% from the target value- were excluded prior to calculating the mean, CV% and bias%. Performance comparisons between different concentration samples were performed with Wilcoxon test considering a significance of 5%. Results: During the study period, an average of 41 laboratories participated (range: 26–49). A total of 17 different types of equipment and 9 distinct methodologies were used. From 2022 onwards, a noticeable shift in equipment and/or methodology was observed among several participants. Notably, five laboratories consistently submitted results for all samples throughout the study. There was no significant difference in the mean CV% between pathological samples (CV% = 5.1) and non-pathological samples (CV% = 5.7), with a p-value of 0.151. Similarly, no significant difference was observed in Bias% between pathological samples (Bias% = 1.0) and non-pathological samples (Bias% = 1.6), with a p-value of 0.069. Before pandemic period (2017-2019), the mean bias% was 0.02, in the pandemic period (2020-2021) was 3.18, and after pandemic 1.43. Based on the minimum EFLM quality specifications for HbA1c bias (2,7%), the mean bias of participants meets the established criteria in 13 samples. Regarding the desirable specification (1.8%), 10 samples and regarding the optimal specification (0.9%), 5 samples were compliant. During the pandemic period, 3 samples did not meet the minimum specifications. Conclusion: During the study period, the laboratories changed equipment without showing performance improvements. There is clear sign of a decline in performance in the pandemic period (2020-2022) with no improvement to the level of pre pandemic period. Most samples met the minimum quality specifications for HbA1c bias established by the EFLM, with a substantial proportion also meeting desirable and optimal targets. These findings highlight the effectiveness of the EurA1c external quality assessment framework in supporting continuous quality improvement in HbA1c testing across Portuguese laboratories.engHBA1CEurA1cExternal Quality AssessmentAnalytical PerformanceEQALMPNAEQPortugalAvaliação Externa da Qualidadeconference object