Higher HbA1c and/or glucose levels alter the association patterns between glycated hemoglobin and fasting glucose levels.

AIMS: To verify the correlations between HbA1c and fasting glucose levels.

METHODS: A cross-sectional study with 14,249 Chinese subjects. Objective was evaluated in pooled, age-stratified, HbA1c and fasting glucose-stratified populations.

RESULTS: In pooled populations, the Pearson correlation coefficients (PCCs) of males and females were 0.684 (P < 0.001) and 0.800 (P < 0.001), respectively. HbA1c and fasting glucose maintained significant correlations within the group with HbA1c < 6.5% and glucose <7.0 mmol/L and the group with HbA1c ≥ 6.5% and glucose ≥7.0 mmol/L in both males (PCC: 0.342, P < 0.001; and PCC: 0.765, P < 0.001, respectively) and females (PCC: 0.318, P < 0.001 and PCC: 0.788, P < 0.001, respectively). The slopes increased from the group with HbA1c < 6.5% and glucose <7.0 mmol/L to the group with HbA1c ≥ 6.5% and glucose ≥7.0 mmol/L in both males (0.26-0.44) and females (0.31-0.46). Linear regression analysis showed that fasting glucose and age were two common factors positively associated with HbA1C, and red blood cell count and red cell distribution width were two common factors negatively associated with HbA1c in both males and females with HbA1c < 6.5% and glucose <7.0 mmol/L. The correlations changed dramatically in the groups with HbA1c ≥ 6.5% and glucose <7.0 mmol/L and HbA1c < 6.5% and glucose ≥7.0 mmol/L.

CONCLUSIONS: High HbA1c and fasting glucose levels greatly altered the associations between HbA1c, glucose and age.