Four RCTs were included in the review (n=1,321 participants). Allocation concealment and double-blinding were adequate in all trials. Randomisation was adequate in two trials and not reported in two. Drop-out rates ranged from 9 to 30%.
There was a statistically significant reduction in glycated haemoglobin A1c compared with baseline in the groups treated with pioglitazone (WMD -1.22%, 95% CI -1.44 to -1.01). There was statistically significant heterogeneity (p<0.001).
Fasting blood glucose was significantly reduced compared with baseline in the pioglitazone-treated groups (reduction of 1.63mmol/L, 95% CI 0.75 to 2.50), with significant heterogeneity (p<0.001).
There was also a reduction of daily insulin doses compared with baseline by between 3 and 12U/day in pioglitazone arms.
Compared with baseline, lipid parameters showed an increase in both low-density lipoprotein cholesterol (0.13 mmol/L, 95% CI 0.09 to 0.17) and high-density lipoprotein cholesterol (0.21mmol/L, 95% CI 0.13 to 0.28) and a reduction in triglycerides (0.05mmol/L, 95% CI 0.01 to 0.09); there was significant heterogeneity in the high-density lipoprotein cholesterol analysis (p<0.001).
There were statistically significant increases in hypoglycaemia (RR 1.57, 95% CI 1.12 to 2.20) and oedema (RR 2.42, 95% CI 1.67 to 3.50).