Performance evaluation of quantitative hemoglobin A2 and fetal hemoglobin testing using commercially lyophilized vs. in-house whole blood controls in Chinese clinical laboratories: a 12-year analysis of National External Quality Assessment Data.

Objectives: To analyze the performance of laboratories in the China National External Quality Assessment Scheme (China NEQAS) for HbA₂ and HbF testing, and to propose strategies for quality improvement.

Methods: Data were obtained from China NEQAS from 2013 to 2024 using both commercially lyophilized controls and in-house whole blood controls. The distributions of methods and instruments were analyzed. Inter-laboratory coefficient variations (CVs) and target values were compared between two types of controls and between method-instrument platforms over 12 years.

Results: The in-house controls remained homogeneous and stable for almost one month at 2-8 °C and for one year at -80 °C. Capillary electrophoresis (CE) became the dominant method, adopted by 84.3 % of labs in 2024. For HbA₂, two EQA controls had comparable concentration ranges and inter-laboratory CVs. HbF in-house controls covered broader pathological concentrations than commercial ones. CE demonstrated lower inter-laboratory CVs for both analytes: HbA₂ was 2.1 ± 1.8 % vs. 5.5 ± 4.8 % (high-performance liquid chromatography, HPLC) and 6.5 ± 4.1 % (agarose gel electrophoresis, AGE), while HbF was 3.2 ± 1.9 % vs. 5.0 ± 1.6 % (HPLC) and 8.6 ± 6.8 % (AGE). Significant discrepancies in maximum-to-minimum mean concentrations were observed among different method-instrument platforms when testing the same controls (up to 10 % for HbF).

Conclusions: In-house controls demonstrate homogeneity, stability and intrinsic commutability, and have an expanded concentration range, can serve as a reliable alternative to commercial controls for EQA. High-precision techniques such as CE should be favoured. Furthermore, the development of reference methods and commutable reference materials is essential for standardization.