210-LB: Evaluation of Two Commercially Available Glycated Hemoglobin Methods

HbA1c level reflects chronic glycemic status if reliable tests are used. The HbA1c testing improved with the efforts of many national and international organizations; however, in some regions, high performing assays might not be readily available. Here we report a comparison study of two immunoassay methods with a high-performance liquid chromatography (HPLC) assay, all of them available in Ecuador. We studied 114 fresh whole-blood samples from adults with normal and pathological HbA1c levels. HbA1c was measured in all samples by DCA-Vantage point-of-care analyzer, I-Chroma portable fluorescent scanner immunoassay and BioRad Variant II Turbo HPLC. Blood samples with variants of hemoglobin were excluded. HbA1c values were expressed in National Glycohemoglobin Standardization Program percentages and mmol/mol, as mean ± standard deviation.

Results: HbA1c measurements by HPLC and DCA-Vantage were similar: 6.3±1.7% (45±18.6 mmol/mol) vs. 6.3±1.8% (45±19.7 mmol/mol), respectively, P=0.057, while HbA1c values by I-Chroma were lower than HPLC, 5.8±1.9% (40±20.8 mmol/mol), P<0.001. Interestingly, the coefficient of variation was below 2% for high and low HbA1c levels, in all methods studied, demonstrating high precision. HbA1c values by HPLC and DCA-Vantage were highly correlated, Kendall's Correlation Coefficient [KCC]: 0.817, whereas the correlation among HPLC and I-chroma was weak, KCC: 0.294. The mean bias between DCA-Vantage and HPLC was -0.02±0.29% (-0.2±3.2 mmol/mol), 95% Confidence Interval of the differences (CID) [0.55%, -0.60%] (6.0 mmol/mol, -6.6 mmol/mol) while for I-Chroma and HPLC the mean bias was -0.50±1.62% (-5.5±17.7 mmol/mol), 95% CID [2.74%, -3.74 %] (30 mmol/mol, -40.9 mmol/mol). Conclusion: HbA1c results by DCA-Vantage were comparable to HPLC, showing a good correlation, an appropriate precision and a low bias. While I-Chroma assay was precise but inaccurate. Our results suggest a significant need for improvement in HbA1c immunoassays currently in use in our country, Ecuador.