Analytical verification and quality assessment of the Tosoh HLC-723GX HbA_1c analyzer

Ion-exchange high-performance liquid chromatography (IE-HPLC) has long been used as a reproducible and versatile analytical tool for HbA_1c measurement. In this study, we performed analytical verification and quality assessment of the recently introduced small IE-HPLC Tosoh HLC-723GX HbA_1c analyzer, and a comparison of results to immunoassay (IA) and capillary electrophoresis (CE).

The total imprecision of Tosoh HLC-723GX was verified according to CLSI EP15-A2 protocol using commercial control materials (C-QC) and pooled human whole blood samples (HWB). The Sigma metric was used for the evaluation of quality targets. HbA_1c results were compared to automated CE (MiniCap Flex Piercing, Sebia, France) and IA (Tina-quant HbA_1c Gen 2, Cobas Integra 400+, Roche Diagnostics, USA) procedures.

The total imprecision of Tosoh HLC-723GX-HbA_1c for IFCC(mmol/mol) and NGSP(%) units was: 1.91/1.25% (HbA_1c=31 mmol/mol/5.0%) and 0.51/0.63% (HbA_1c=84 mmol/mol/9.8%) for C-QC, and 0.39/0.2% (HbA_1c=47 mmol/mol/6.5%) and 0.77/0.46% (HbA_1c=94 mmol/mol/10.8%) in HWB samples, respectively. Bland-Altman analysis did not reveal any deviation of the results between Tosoh HLC-723GX and CE: mean difference 0.0% (95%CI: -0.02927 to 0.02653%), while the mean HbA_1c difference against IA was -0.07% (95%CI: -0.1039 to -0.02765). At the selected HbA_1c clinical decision level (48 mmol/mol/6,5%), six sigma analysis gave σ value of 3.91, within a desirable classification of performance.

The analytical performance of the Tosoh HLC-723GX complies with the rigorous quality criteria for clinical use of HbA_1c, with the results comparable to the CE procedure. Tosoh HLC-723GX provides a plausible analytical choice for reliable HbA_1c measurement in low-volume laboratories.