| Variable | Categories | n | SSI | SSI Risk (%) | RR | [C.I. 95% R.R.] | p-value |
| Surgical Wound Classification | Contaminatedordirty/infected | 29 | 2.00 | 6.9% | 2.63 | [0.67; 10.35] | 0.183 |
| Clean or clean-contaminated | 1602 | 42.00 | 2.6% | ||||
| American Society of Anesthesiologists (ASA) | >2 | 321 | 16.00 | 5.0% | 2.29 | [1.25; 4.18] | 0.011 |
| ≤2 | 1286 | 28.00 | 2.2% | ||||
| Type of Surgery | Emergency | 83 | 4.00 | 4.8% | 1.96 | [0.71; 5.36] | 0.164 |
| Elective | 1501 | 37.00 | 2.5% | ||||
| General Anesthesia | Yes | 697 | 29.00 | 4.2% | 1.88 | [1.09; 3.24] | 0.029 |
| No | 993 | 22.00 | 2.2% | ||||
| Prophylactic Antibiotic | Yes | 772 | 39.00 | 5.1% | 0.41 | [0.18; 0.93] | 0.045 |
| No | 49 | 6.00 | 12.2% | ||||
| Trauma Surgery | Yes | 136 | 4.00 | 2.9% | 1.27 | [0.46; 3.52] | 0.558 |
| No | 1422 | 33.00 | 2.3% | ||||
| NNIS Risk Index | 0 | 1017 | 13.00 | 1.3% | - | - | <0.001 |
| 1 | 329 | 15.00 | 4.6% | ||||
| 2 | 20 | 3.00 | 15.0% | ||||
| Length of Hospital Stay Before Surgery (Days) | >4 | 187 | 12.00 | 6.4% | 2.18 | [1.19; 3.99] | 0.016 |
| ≤4 | 1974 | 58.00 | 2.9% | ||||
| Number of Professionals at Surgery | >2 | 234 | 14.00 | 6.0% | 2.73 | [1.51; 4.93] | 0.003 |
| ≤2 | 1822 | 40.00 | 2.2% | ||||
| First Hospital Admission | Yes | 1750 | 53.00 | 3.0% | 0.73 | [0.43; 1.25] | 0.277 |
| No | 411 | 17.00 | 4.1% | ||||
| Age (Years) | >60 | 1377 | 43.00 | 3.1% | 0.91 | [0.56; 1.46] | 0.705 |
| ≤60 | 784 | 27.00 | 3.4% | ||||
| Duration of Surgery (Hours) | >2 | 1003 | 33.00 | 3.3% | 1.14 | [0.64; 2.0] | 0.770 |
| ≤2 | 621 | 18.00 | 2.9% |