(a) Subgroup comparisons for Helicobacter pylori infection on the risk of esophageal squamous cell carcinoma
| Subgroup | No. of studies | I 2 (%) | Overall OR (95% CI) | P value§ | |
|---|---|---|---|---|---|
| DL | HKSJ | ||||
| Esophageal squamous cell carcinoma | |||||
| Case/control (2,063/35,051) | |||||
| All studies | 21 | 78.5 | 0.84 (0.64, 1.09) | 0.74 (0.54, 0.97) | |
| Ethnicity | 0.144 | ||||
| Caucasians | 11 | 70.8 | 0.80 (0.54, 1.17) | 0.73 (0.48, 1.11) | |
| Mongolians | 8 | 86.9 | 0.89 (0.56, 1.41) | 1.13 (0.79, 1.60) | |
| Negroes | 1 | — | 0.34 (0.07, 1.58) | — | |
| Australian | 1 | — | 1.18 (0.84, 1.65) | — | |
| Study area | <0.001∗ | ||||
| North America | 2 | 0 | 1.83 (1.17, 2.87) | 1.79 (0.25, 12.9) | |
| East Asia | 8 | 86.9 | 0.89 (0.56, 1.41) | 1.13 (0.79, 1.60) | |
| Europe | 7 | 0.9 | 0.84 (0.65, 1.10) | 0.72 (0.46, 1.12) | |
| Middle East | 3 | 0 | 0.34 (0.22, 0.52) | 0.34 (0.26, 0.44) | |
| Oceania | 1 | — | 1.18 (0.84, 1.65) | — | |
| Study type | 0.250 | ||||
| Case-control | 19 | 80 | 0.85 (0.65, 1.13) | 0.70 (0.51, 0.97) | |
| Cohort | 2 | 49 | 0.59 (0.19, 1.86) | 0.80 (0.0, 967.18) | |
| Study object | 0.005∗ | ||||
| Population-based studies | 14 | 79.5 | 0.93 (0.68, 1.28) | 0.91 (0.66, 1.24) | |
| Clinical-based studies | 7 | 72.5 | 0.66 (0.40, 1.07) | 0.53 (0.28, 0.99) | |
| Matching | 0.290 | ||||
| Studies with matched controls | 2 | 86.5 | 0.87 (0.30, 2.52) | 1.14 (0.0, 563.04) | |
| Studies without matched controls | 19 | 78.7 | 0.83 (0.63, 1.11) | 0.71 (0.52, 0.96) | |
| Helicobacter pylori detection method | 0.003∗ | ||||
| Serology | 16 | 81.4 | 0.83 (0.61, 1.12) | 0.83 (0.61, 1.14) | |
| Rapid urease test | 2 | 0 | 0.39 (0.22, 0.69) | 0.35 (0.17, 0.69) | |
| Serology, histology, and rapid urease test | 3 | 0 | 1.32 (0.87, 2.01) | 1.33 (0.72, 2.44) | |
Note: DL: DerSimonian-Laird; HKSJ: Hartung-Knapp-Sidik-Jonkman. §Differences between subgroups; ∗the difference was statistically significant.