Table 4.

Logistic regression analysis of risk factors for SSIs in the alternative model and NNIS and SENIC indexes

Index, variable	β	p value	RR (95% CI)
Alternative model
ATI	0.993	0.001	2.70 (1.51–4.84)
Contamination	1.170	< 0.001	3.22 (1.74–5.98)
Admission to ICU	1.811	< 0.001	6.12 (3.35–11.16)
NNIS index
Type of wound	1.173	< 0.001	3.23 (1.82–5.73)
ASA	0.742	0.003	2.10 (1.28–3.44)
Surgical time	0.566	0.028	1.76 (1.06–2.92)
SENIC index
Type of wound	1.104	< 0.001	3.02 (1.70–5.37)
No. of injured organs	0.755	0.002	2.13 (1.31–3.47)

ASA = American Society of Anesthesiology; ATI = abdominal trauma index; CI = confidence interval; ICU = intensive care unit; NNIS = National Nosocomial Infections Surveillance;⁷,⁸ RR = relative risk; SENIC = Efficacy of Nosocomial Infection Control;⁹,¹⁰ SSI = surgical site infection.