Achieving comparability with IFCC reference method for the measurement of hemoglobin A by use of an improved isotope-dilution mass spectrometry method.

Liu, Hong; Wong, Lingkai; Yong, Sharon; Liu, Qinde; Lee, Tong Kooi

The development of reference measurement methods for hemoglobin A (HbA) is important for quality assurance in diabetes management. The IFCC reference method using purified proteins as calibration standards is the recommended accuracy-based reference method for the standardization of HbA measurement. We developed a highly precise and accurate liquid chromatography-isotope-dilution tandem mass spectrometry (LC-IDMS/MS) procedure, which can serve as an alternative accuracy-based method for HbA measurement. In this method, enzymatic proteolysis was applied to sample preparation, followed by LC-IDMS/MS measurement of hemoglobin A (HbA) and HbA, using two 'signature' hexapeptides for calibration. The concentrations of the signature hexapeptide calibration solutions were, in turn, determined using a hydrolysis method with HCl, followed by LC-IDMS/MS measurement using amino acid solutions as calibration standards. These solutions were gravimetrically prepared from pure amino acid certified reference materials (CRMs). The developed LC-IDMS/MS method was used in participation in an IFCC ring trial for reference laboratories (RELA 2013 and 2014) for HbA, where our results were compared with those using the IFCC reference method. The deviations were found to be 0.4-1.7 mmol mol [or 0.04-0.16 % in National Glygohemoglobin Standardization Program (NGSP) units], revealing good comparability with the IFCC reference method. The relative expanded uncertainty of the LC-IDMS/MS was in the range of 2.6 % to 2.8 % (1.6 % to 2.2 % after converting to NGSP units). With excellent method precision, good comparability with the IFCC reference method, and a small measurement uncertainty, the developed LC-IDMS/MS method may be used as an alternative accuracy-based reference method for HbA measurement. [Figure not available: see fulltext.]

HEMOGLOBINS; MASS spectrometry; TREATMENT of diabetes; MEDICAL quality control; CALIBRATION

Analytical & Bioanalytical Chemistry, 2015, Vol 407, Issue 25, p7579

1618-2642

Academic Journal

10.1007/s00216-015-8961-2