In total, 218 RCTs (approximately 78,000 participants) were included in the review; number of participants per study arm ranged from 30 to 2,493. Double-blind procedures were reported by 120 trials and triple-blind procedures reported by two trials. One trial reported a single-blind procedure; the remaining trials had open-label designs. No other quality assessment findings were reported.
The proportion of participants who achieved the HbA1c goal of less than 7% ranged from 25.9% (95% CI 18.5 to 34.9) with alpha-glucosidase inhibitors to 63.2% (95% CI 54.1 to 71.5) with exenatide long action release. Mean changes (reductions) from baseline HbA1c ranged from -0.64% (SD=0.20) for glinides to -1.91% (SD=0.63) for biphasic insulin. Significant statistical heterogeneity was found for all classes of antidiabetic drugs (all Ι² values exceeded 80%).
Multivariate meta-regression analysis did not indicate significant roles for drug user status, gender, mean age, year of publication, trial duration and concomitant drug use. A progressive decrease in the proportion of participants at target for each 0.5% increase in baseline HbA1c was observed.