Reference intervals of HbA1c and fasting plasma glucose for pregnant women in Chongqing and the value of their combination in screening gestational diabetes mellitus

Abstract

Objective To establish the reference intervals of hemoglobin A1c(HbA1c) and fasting plasma glucose(FPG) in the first and second trimester of pregnancy in Chongqing , and to evaluate the viability of the combination of HbA1c and FPG in screening gestational diabetes mellitus (GDM). Methods The study retrospectively selected the pregnant women seen at the Department of Obstetrics and Gynecology in Daping Hospital between September 2014 and August 2015. The results of FPG during 10-13 pregnant weeks and 75 g oral glucose tolerance test (OGTT) and HbA1c during 24-28 pregnant weeks were available.Totally 185 cases were assigned into GDM group, and 269 cases were assigned into normal group based on the American Diabetes Association (ADA) guidelines. Reference intervals of HbA1c and FPG in normal pregnant woman were developed. The difference of HbA1c, FPG and OGTT results between two groups was analyzed. T-student test, NcMemar test, signed rank sum test, ROC curve were used for statistical analysis. Results The reference intervals of HbA1c and FPG in first and second trimester were 4.58%-5.52%, 4.21-5.49 mmol/L and 4.03-5.08 mmol/L.The FPG level in first and second trimester and HbA1c level in GDM group vs normal group were(5.06±0.37) vs(4.85±0.32)mmol/L(t=6.569, P=0.000), 5.23(5.11, 5.4) vs 4.74(4.54, 4.91) mmol/L(z=-14.31, P=0.000)and 5.3(5.1, 5.4)% vs 5.2(5.0, 5.3)%(z=-5.79, P=0.000)respectively. The area under receiver operating characteristic curve (ROC) of HbA1c, and FPG in first and second trimester was 0.655, 0.659 and 0.890 respectively. When the cut-off value of HbA1c was 5.35%, the AUC of the combination of HbA1c and FPG in second trimester was 0.898, the sensitivity was 0.838, and the specificity was 0.859.The kappa coefficient for identifying GDM between OGTT and the combined method was 0.692(P=0.000). Conclusion HbA1c combined with FPG is of some value in screening GDM.(Chin J Lab Med, 2016, 39: 413-417) Key words: Diabetes, gestational; Hemoglobin A, glycosylated; Blood glucose; Reference values