Table 2. Subgroup analysis for β-cell function related to HOMA-β and PI/IR.
| Subgroup | No. studies | N | WMD | 95%CI |
| HOMA-β (monotherapy) | ||||
| Metformin | 4 | 1457 | 18.01% | (11.09%,24.94%) |
| Sitagliptin | 8 | 1553 | 11.29% | (9.21%,13.37%) |
| Pioglitazone | 3 | 395 | 16.06% | (9.67%,22.44%) |
| HOMA-β (combination therapy) | ||||
| Metformin+sitagliptin | 5 | 1371 | 40.23% | (32.30%,48.16%) |
| Metformin+pioglitazone | 3 | 305 | 9.81% | (1.67%,17.95%) |
| Sitagliptin+pioglitazone | 2 | 250 | 11.82% | (6.61%,17.04%) |
| PI/IR (monotherapy) | ||||
| Metformin | 4 | 1420 | −0.137 | (−0.082,−0.192) |
| Sitagliptin | 5 | 1199 | −0.064 | (−0.036,−0.092) |
| Pioglitazone | 3 | 329 | −0.068 | (−0.044,−0.093) |
| PI/IR (combination therapy) | ||||
| Metformin+sitagliptin | 4 | 1199 | −0.177 | (−0.118,−0.237) |
| Metformin+pioglitazone | 3 | 305 | −0.038 | (−0.005,−0.071) |
| Sitagliptin+pioglitazone | 2 | 250 | −0.080 | (−0.045,−0.114) |
WMD: weighted mean difference; CI: confidence interval.