Detection of a novel hemoglobin variant Hb Liaoning by matrix assisted laser desorption/ionization-time of flight mass spectrometry

Comparability of different methods of glycated hemoglobin measurement for samples of patients with variant and non-variant hemoglobin

BACKGROUND

Glycated hemoglobin (e.g., HbA_1c) is measured to monitor patients with diabetes. However, the measurement results can vary according to the analysis method and presence of variant hemoglobin. Thus, we compared HbA_1c results between liquid chromatography-tandem mass spectrometry (LC-MS/MS) as the reference method and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS).

METHODS

%HbA_1c were measured using the 2 methods in 45 non-variant and 73 heterozygous variant samples. Precision was calculated; the results were compared using Passing-Bablok regression and the concordance correlation coefficient (CCC). The average bias between methods was compared with the lowest bias of 2.3% for biological variation.

RESULTS

The precision of the 2methods was <2%. The R² for the non-variant samples were 0.986 and the CCC was 0.99. Based on α- and β-chain, the variant samples were divided into 4 groups: α-chain, α-chain negligible, β-chain, and β-chain negligible variants. The R² between the 2 methods of the 4 groups were ＞0.95; However, the average biases of α-chain and β-chain variants were above the minimum bias.

CONCLUSION

LC-MS/MS and MALDI-TOF MS had good comparability in the measurement of HbA_1c in non-variant samples, but the existence of variant hemoglobin caused discrepancies.

Comparison of glycation degrees of HbG-Coushatta and HbG-Taipei with HbA using liquid chromatography with tandem mass spectrometry

BACKGROUND

Hemoglobin A_1c(HbA_1c) is widely used to measure glycemic status and control in diabetes testing and treatment and is an important risk factor forcomplications of diabetes. Hemoglobin variants can interfere with the HbA_1c testing method by reducing the life span of erythrocytes or due to differences in glycation degrees. In this study, glycation levels of the HbA, HbG-Coushatta, and HbG-Taipei β-chains (βA, βG-Coushatta, and βG-Taipei, respectively) were examined.

METHODS

Blood samples from heterozygotic patients (HbG-Coushatta/HbA, HbG-Taipei/HbA) were analyzed. Glycation rateswere determined using high-performance liquid chromatography with tandem mass spectrometry. Ratios of glycated βG-Coushatta to glycated βA and glycated βG-Taipei to glycated βA were calculated by comparingareas under the curves from extracted ion chromatograms.

RESULTS

βG-Coushatta and βG-Taipei were 6.08 ± 1.38% and 5.95 ± 0.93% glycated (respectively), which were significantly higher than βA chains(4.55 ± 1.30% and 4.51 ± 0.91%, respectively; p = 0.000). The total glycation degree (α + β) in HbG-Coushatta and HbG-Taipei heterozygotes were estimated to be 9% and 8% higher than those of HbA homozygotes (P＜0.001), respectively.

CONCLUSION

βG-Coushatta and βG-Taipei glycation degrees were significantly higher than βA, while the differences in total hemoglobin (α + β) were small and unlikely to impact the clinical interpretation of HbA_1c results.