Coefficients of variation analyses of internal quality control status for blood lead in China from 2015 to 2023

Background Blood lead test is widely conducted in Chinese laboratories, while the imprecision of blood lead measurement based on internal quality control (IQC) across China has not been comprehensively evaluated nowadays. Methods Using the IQC data of blood lead collected through a web-based external quality assessment (EQA) reporting system, we analysed current coefficients of variation (CVs) of blood lead from 2015 to 2023 among Chinese laboratories. Two allowable total error (TEa) imprecision levels from EQA were applied to calculate the pass rates, namely percentages of laboratories meeting precision quality specifications. Besides, CV values and pass rates by different subgroups were further performed to assess potential differences. Results Generally, median CV values significantly declined year by year from 6.8% in February 2015 to 5.9% in March 2023. The pass rates based on 1/3 TEa showed upward trends increasing from 15.3% in February 2015 to 20.0% in March 2023, but these percentages were non-ideal with less than 25%. No significant differences in CVs were found between tertiary hospitals and non-tertiary hospitals and between accredited and non-accredited laboratories. Significant time trends were observed in tertiary hospitals and non-accredited laboratories. As for manufacturers, Bohui and self-made QC sample were most widely used with obvious interannual declining trends of CVs. Conclusions The CVs of blood lead demonstrated continuous overall improvements in the past twenty years. However, relatively lower pass rates indicated the non-ideal imprecision performance, and more proper performance specifications are warranted. Thus, imprecision improvement and ongoing investigation for blood lead IQC are still needed.