Table 2.
Subgroup analysis of the included studies.
| Subgroups | No. of studies | SMD (95% CI) | P | Test of heterogeneity | |
|---|---|---|---|---|---|
| I 2 | P | ||||
| Serum | |||||
| Study location | |||||
| Asia | 13 | 0.74 (0.42-1.07) | <0.001 | 91.3% | <0.001 |
| Europe | 5 | 0.39 (−0.20-0.98) | 0.199 | 81.5% | <0.001 |
| Africa | 1 | 3.22 (2.06-4.38) | <0.001 | / | / |
| Study design | |||||
| Cross-sectional | 12 | 0.91 (0.54-1.29) | <0.001 | 92.5% | <0.001 |
| Case-control | 6 | 0.13 (−0.11-0.36) | 0.283 | 25.0% | 0.246 |
| Cohort | 1 | 3.22 (2.06-4.38) | <0.001 | / | / |
|
| |||||
| Plasma | |||||
| Study location | |||||
| Asia | 7 | 0.09 (−0.14-0.31) | 0.463 | 93.7% | <0.001 |
| Europe | 2 | 0.54 (−0.21-1.29) | 0.156 | 0.0% | 0.729 |
| South America | 1 | −0.12 (−0.84-0.59) | 0.734 | / | / |
| Study design | |||||
| Cross-sectional | 8 | 0.54 (−0.12-1.20) | 0.108 | 91.7 | <0.001 |
| Case-control | 1 | −0.38 (−0.88-0.12) | 0.557 | / | / |
| Cohort | 1 | 0.07 (−0.17-0.31) | 0.133 | / | / |