Does serum 1,5-anhydroglucitol establish a relationship between improvements in HbA_1c and postprandial glucose excursions? Supportive evidence utilizing the differential effects between biphasic insulin aspart 30 and insulin glargine

Aim: To investigate the relationship between changes in glycated haemoglobin (HbA_1c) and postprandial glucose excursions on 1,5-anhydroglucitol (1,5-AG) in patients with Type 2 diabetes, utilizing the differential effects between biphasic insulin aspart 30 (BIAsp 30) or insulin glargine (IGlar) on postprandial glucose (PPG) levels. Methods: 1,5-AG was measured using the GlycoMark® assay at baseline and after 12 and 28 weeks in the INITiation of Insulin to reach HbA_1c Target (INITIATE) study of 233 patients randomized to either BIAsp 30 or IGlar. Results: Baseline 1,5-AG was low and not significantly different (4.9 ± 3.5 and 4.3 ± 2.6 μg/ml in the BIAsp 30 and IGlar groups, respectively). After 28 weeks, the levels of 1,5-AG were higher in the BIAsp 30 than in the IGlar group (13.4 vs. 11.1 μg/ml, P = 0.008) and change from baseline was 25% greater with BIAsp 30 than IGlar (8.4 vs. 6.7 μg/ml, P = 0.011). 1,5-AG levels increased as a function of decreasing HbA_1c or the average change in postprandial plasma glucose (PPG_ave) with significant relationships for 1,5-AG/ HbA_1c vs. HbA_1c or 1,5-AG/PPG_avevs. PPG _ave (both P < 0.0001), respectively. Conclusions: As reported in previous publications, 1,5-AG reflects ambient glycaemic control and increases with reductions in HbA_1c and postprandial glucose. The greater reductions in postprandial excursion achieved with BiAsp 30 compared with glargine were associated with greater increases in 1,5-AG. Even moderate elevations in HbA_1c substantially lower 1,5-AG, suggesting that it can be most discriminating in identifying patients with excessive postprandial glucose excursions at HbA_1c levels that approach the upper end of the normal range.