Hemoglobin A(1c) Reporting Units and Diagnostic Cut-Offs in Relation to International Recommendations

Abstract

Purpose. In this account were studied the use of units and cutoff limits for hemoglobin A(1c) in worldwide clinical laboratory practice and the quality assurance ranges of hemoglobin A(1c) by calculating the target limits from the values of Labquality Ltd. and ERLGH. Methods. The use of HbA(1c) units and the diagnostic limits for diabetes were examined using e-mail and letter inquiries to 37-51 societies of laboratory medicine (mainly clinical chemistry) sent from 2009 to 2017. The parametric statistical programs of Labquality Ltd., SPSS ® 13.0, and MS Excel 2013 (Microsoft ® Co., Cambridge, MA, USA) were used. Results. The mean values of the Finnish quality control organization Labquality Ltd. and the corresponding values from the HbA(1c) queries as to the percentage and mmol/mol SI units (IFCC) were used. The IFCC system for hemoglobin A(1c) is slowly but constantly gaining acceptance in Europe, but remains quite rare outside Europe where the percentage results were correspondingly lower. The mean round values of Labquality Ltd. and the corresponding mean values of the European Reference Laboratory for Glycohemoglobin (ERLGH) showed equal ranges for calculation of the target values with ± 6% intervals for the percentage results and ± 8% intervals for the mmol/mol results. Conclusions. To avoid confusion, the overall use of mmol/mol as a single unit for HbA(1c) may be the best option when the IFCC system has been accepted worldwide. The target values can be calculated equally well from the mean values of Labquality Ltd. and the ERLGH values in terms of both per percentage and mmol/mol units.