Table 4.
Relative risk of postoperative infection based on timing of process improvements, after adjusting for sex, age, urgency, wound class and hospital using modified robust Poisson regression
| Relative risk | P | |
|---|---|---|
| Infection | ||
| Baseline | 1·00 (reference) | |
| After implementation | 0·65 (0·43, 0·99) | 0·043 |
| Sex | ||
| F | 1·00 (reference) | |
| M | 0·83 (0·52, 1·32) | 0·429 |
| Age (years) | ||
| ≤ 25 | 1·00 (reference) | |
| 26–30 | 0·72 (0·45, 1·15) | 0·169 |
| 31–40 | 0·81 (0·50, 1·30) | 0·382 |
| ≥ 41 | 0·82 (0·46, 1·47) | 0·511 |
| Urgency | ||
| Elective | 1·00 (reference) | |
| Emergency | 1·10 (0·70, 1·74) | 0·683 |
| Wound class | ||
| Clean | 1·00 (reference) | |
| Clean contaminated | 0·38 (0·08, 1·68) | 0·202 |
| Contaminated | 0·84 (0·18, 3·87) | 0·827 |
| Dirty | 2·01 (0·44, 9·22) | 0·367 |
| Type of operation | ||
| Ear, nose and throat | 1·00 (reference) | |
| Orthopaedic | 4·44 (0·63, 31·19) | 0·134 |
| Soft tissue | 3·72 (0·92, 15·09) | 0·066 |
| Gynaecological | 4·36 (0·62, 30·44) | 0·138 |
| Vascular | 1·22 (0·12, 12·27) | 0·867 |
| Appendicectomy | 4·73 (0·76, 29·63) | 0·097 |
| Cholecystectomy | 9·89 (1·20, 81·43) | 0·033 |
| Colorectal | 10·93 (1·76, 67·92) | 0·010 |
| Caesarean | 11·09 (1·82, 67·74) | 0·009 |
| Hernia | 2·31 (0·40, 13·34) | 0·348 |
| Hysterectomy | 12·09 (1·63, 89·57) | 0·015 |
| Gastrointestinal/laparotomy | 5·48 (0·96, 31·31) | 0·056 |
| Urological | 3·92 (0·30, 50·67) | 0·295 |
Values in parentheses are 95 per cent confidence intervals. Relative risks by hospital are not shown.