Estimating HbA1c from timed Self-Monitored Blood Glucose values.

AIMS

To analyze mathematical relationships between timed Self-Monitored Blood Glucose (SMBG) and HbA1c, and to identify the SMBG values that correlate most strongly with HbA1c.

METHODS

We utilized the average premeal (Pre) and 90-min postmeal (Post) SMBG results from 547 A1c-Derived Average Glucose (ADAG) study participants (285 type 1, 178 type 2 and 84 non-diabetic) to analyze the mathematical relationships with HbA1c levels. Specific times of daily SMBG that best correlate with HbA1c were identified.

RESULTS

Linear regression analyses showed the following correlations for Pre and Post, Pre only and Post only, respectively: HbA1c = 2.488 + 0.018 × Pre + 0.012 × Post, R = 0.741, P < 0.0001; HbA1c = 2.887 + 0.029 × Pre, R = 0.695, P < 0.0001; and HbA1c = 2.815 + 0.025 × Post, R = 0.657, P < 0.0001. Among patients with type 2 diabetes mellitus (DM), of the 6 individual timepoints, pre-dinner SMBG had the strongest correlation with HbA1c (R = 0.577). This was followed by pre-breakfast (R = 0.562). Examining combinations of timepoints revealed that pre-breakfast + pre-dinner (R = 0.666) performed similarly to the full 6-timepoints (pre-meals + post-meals, R = 0.712).

CONCLUSIONS

We have established mathematical relationships between HbA1c and timed SMBG values and identified pre-dinner and pre-breakfast as the two SMBG timepoints that best correlate with HbA1c in patients with type 2 DM.