Abstract

Using appropriate statistical tests and taking into account the analytical performance of hemoglobin A_1c (HbA_1c) measurements, is it useful to establish HbA_1c age-related values in non-diabetic subjects? Non-diabetic subjects (n=135, 72 women and 63 men) from the neuromuscular department of the Pitié-Salpétrière Hospital (Paris) were involved in our study. Subjects were divided into two groups related to age: 51 patients under 50 years old and 84 subjects aged 50 years or more.

Fasting plasma glucose and HbA_1c measurements were respectively performed by enzymatic assay using the hexokinase method and high-performance liquid chromatography based on the ion exchange methodology with high precision.

We first checked the normality of HbA_1c distribution using the Kolmogorov-Smirnov test. Then we compared mean HbA_1c in the two age subgroups using the Student's t test. Mean HbA_1c was significantly (p<0.0001) higher in the subgroup aged 50 years or more (mean HbA_1c=5.2%) than in younger subjects (mean HbA_1c=5.0%). Then plots were drawn to check the relationship between HbA_1c and age. Under the hypothesis of linearity, determination coefficients (R²) were calculated. However, considering their low values, this hypothesis must be rejected and other factors than age must be retained to explain HbA_1c variability.