Table 6: Hierarchical multivariate regression analysis models of risk factors for SSIs at the study area 2011.
R2! using Nagelkerke likelihood ratio, * P< 0.05, ** P <0.01
Steps Variables entered Odds ratio (95% confidence intervals)
Model 1 Model 2 Model 3
1- Basic patients characteristics - Age (≥ 60 years)
- Gender (female)
- Education (≥ 12 years)
- Chronic morbidity (yes)
- Body mass index (≥ 30) 		1.62(1.02-2.54)*
1.39(1.08-1.79)*
1.41(1.23-1.76)*
3.11(2.11-4.58)**
1.82(1.13-2.94)** 		1.39(0.83-2.33)
1.34(0.81-2.22)
1.33(0.93-1.92)
1.79(1.17-2.74)**
1.54(1.31-1.93)* 		1.31(0.81-2.13)
1.29(0.78-2.13)
1.30(0.91-1.86)
1.54(1.31-1.93)*
1.41(0.98-2.04)
2- Peri-operative conditions - Type of surgery (emergency)
- ASA score (≥ 3)
- Wound class (contaminated-dirty) 		4.79(3.91-5.87)**
2.18(1.28-3.72)**
8.87(6.21-12.66)** 		2.18(1.42-3.34)**
1.83(1.24-2.70)*
5.62(4.08-7.73)**
3- Post-operative conditions - Operative time (≥ 90 minutes)
- ICU admission (yes)
- Presence of drain
- ICU length of stay (≥ 2 days)
- Total hospital length of stay (≥ 6 days). 		1.98(1.34-2.93)*
3.19(2.22-4.59)**
3.02(2.09-4.37)**
1.39(0.83-2.33)
1.34(0.81-2.22)
Constant
R2!
Δχ2
Significance 		14.08
.195
28.17
0.003 		13.25
.216
31.32
0.005 		11.41
.238
34.71
0.091