Adjusted ORs of surgical site infections: analysis of risk factors by logistic regression model using the general estimating equation method
| Basis-odds | Male gender | Age >75th percentile | NNIS risk index 1 | NNIS risk index 2 | NNIS risk index 3 | Department with ≤50 procedures/year | Department with >50 and ≤100 procedures/year | Department with >100 procedures/year | |
| Arthroscopy | 0.000824 | 2.2737 | NA | 2.9244 | 5.1510 | 15.967 | 6.9671 | Reference | 1.1741 |
| Knee replacement | 0.00430 | 1.2397 | 1.1393 | 1.6103 | 3.0021 | 17.477 | 2.3254 | Reference | 1.1376 |
| Hip replacement | 0.00707 | 1.3828 | 1.4730 | 1.5962 | 3.0277 | 6.2507 | 0.8110 | Reference | 0.6159 |
Basic odds give the risk by procedure for individual patients: it is highest for hip replacement and lowest for arthroscopy, and increases if other risk factors are present.
Department with >50 and ≤100 procedures/year were used as reference (=1).
Significant ORs are shown in bold. For year, significance is set at 0.05; all ORs are included in the model.
NA, not applicable; NNIS, National Nosocomial Infection Surveillance System; NNIS risk index is based on wound class, duration of operation and ASA score.