Table 1. The results of pooled incidence of SSI and subgroup analysis by study setting.
| Subgroups | No. of studies | Incidence of ISS% (95% CI) | I2 (%) | P value |
|---|---|---|---|---|
| All studies | 84 | 4.5 (3.1,5.8) | 98.3 | |
| Year | ||||
| Before 2005 | 30 | 4.5 (2.3,6.6) | 95.3 | 0.045 |
| After 2005 | 54 | 3.1 (2.8,3.5) | 98.2 | |
| Region | ||||
| Eastern coastal | 40 | 3.0 (2.4,3.5) | 98.1 | 0.017 |
| Midlands | 24 | 3.8 (1.4,6.7) | 99.1 | |
| Remote western | 18 | 4.6 (4.0,5.1) | 94.9 | |
| Hospital rank | ||||
| Grade III | 64 | 4.3 (2.7,5.9) | 98.7 | 0.793 |
| Grade II | 11 | 3.5 (2.6,4.5) | 95.8 | |
| Surveillance implementation | ||||
| <1 year | 24 | 3.6 (2.9,4.4) | 96.6 | 0.762 |
| 1–3 years | 21 | 2.7 (2.1,3.3) | 97.6 | |
| >3 years | 39 | 5.2 (2.7,7.7) | 99.0 | |
| Surgical procedure | ||||
| General surgery | 45 | 3.1 (1.0,5.2) | 98.9 | 0.004 |
| Abdominal surgery | 15 | 8.3 (6.5,10.0) | 95.6 | |
| Gynaecology & obstetrics | 8 | 5.7 (0.9,13.9) | 93.2 | |
| Neurosurgery | 6 | 3.6 (1.4,5.8) | 93.3 | |
| Thoracic surgery | 5 | 3.0 (2.7,3.3) | 97.7 | |
| Orthopaedic surgery | 4 | 1.0 (0.5,1.6) | 90.3 | |
| Confounding factors control | ||||
| Adjusted* | 53 | 3.6 (1.9,5.3) | 94.8 | 0.815 |
| Crude | 31 | 5.1 (2.5,7.9) |
*The SSI incidence was adjusted by at least one confounding factor.
P values test homogeneity between strata with the Wilcoxon or Kruskal-Wallis non-parametric rank test according to the numbers of strata.
Random effects model was use to pool incidences.