The impact of ferritin on the disassociation of HbA1c and mean plasma glucose

Objective To explore the impact of ferritin level on the disassociation of glycated hemoglobin A1c (HbA1c) and mean plasma glucose (MPG). Reseach Design and Methods We used a 2012-2013 cross-sectional survey conducted in Pinggu district, Beijing including 3095 Chinese participants aged 25-75 years. We categorized their glycemic status by interviewing for diagnosed diabetes and by measuring HbA1c, fasting plasma glucose (FPG), and 2-hours post-load plasma glucose (2-hours PPG). We fitted a multivariable regression model to explore the impact of ferritin on the association of HbA1c or glycated albumin (GA) and mean plasma glucose. Results A total of 5.65% of participants were diagnosed as diabetes using HbA1c criteria, and 9.79% using oral glucose tolerance test criteria. Compared with males, females had significantly lower hemoglobin levels (159.82 +/- 11.56 vs 135.93 +/- 12.62) and lower ferritin levels (113.00 [68.55, 185.50] vs 33.40 [12.40, 70.13]). Linear regression analysis performed in different groups classified by different diagnose criterion indicated that the correlation between MPG and HbA1c differs in different tertiles of ferritin (lowest vs middle vs highest: R-2 = 0.507 vs 0.645 vs 0.687 in female; R-2 = 0.415 vs 0.715 vs 0.615 in male), and the association between MPG and HbA1c diminished in the lowest tertile of ferritin. Conclusions Ferritin level might affect the association between glucose and HbA1c, which should be taken into account when using HbA1c as a diagnosis criterion for diabetes and prediabetes.