Labile A1C Is Inversely Correlated With the Hemoglobin Glycation Index in Children With Type 1 Diabetes

OBJECTIVE

We hypothesized that labile A1C (LA1C) is directly correlated with stable A1C (SA1C) and between-patient differences in SA1C, which are independent of mean blood glucose (MBG).

RESEARCH DESIGN AND METHODS

We measured SA1C, LA1C, MBG, and a single clinic capillary glucose (CCG) from 152 pediatric patients with type 1 diabetes. Patients were grouped as high, moderate, or low glycators by hemoglobin glycation index (HGI).

RESULTS

LA1C and SA1C were correlated with CCG and MBG. LA1C was not correlated with SA1C (r = 0.06, P = 0.453). LA1C level was significantly associated with glycator group status (P < 0.0019) and CCG (P < 0.0001). Adjusted LA1C levels were highest in the low-HGI patients and lowest in the high-HGI group.

CONCLUSIONS

A conventional model of SA1C being directly correlated with LA1C concentration was not confirmed. Between-patient differences in SA1C at the same MBG may be due to complex intracellular factors influencing formation of SA1C from LA1C.Our team and others have described groups of diabetic patients who consistently demonstrate markedly higher (high glycators) or lower (low glycators) A1C despite both groups having similar preceding mean blood glucose (MBG) (1,2). As A1C is formed by the stable Amadori rearrangement of a precursor known as labile A1C (LA1C) (3), we hypothesized that high glycators would also have higher levels of LA1C, compared with low glycators. We tested this hypothesis in a well-characterized group of children with type 1 diabetes.