[Use of the NNIS index for determining the intrinsic risk of surgical infection].
BACKGROUND
To perform valid comparisons of rates of surgical wound infection (SWI) methods of adjustment must be carried out to eliminate the bias produced by the different profile of patients attended.


METHODS
We studied retrospectively the SWI which occurred in 2,651 anaesthetized operations. The rates of SWI were analyzed according to the National Nosocomial Infection Surveillance-derived risk index (NNIS risk index).


RESULTS
The average rate of SWI was 5.1%. The tree components of the NNIS risk index (contaminated or dirty surgical operation, ASA preoperative score > or = 3, time of anaesthesia > of the percentile 75th) were each one independent and they showed similar risks of surgical infection (odds ratio 1.6, 1.9, and 2.1 respectively). The rates of SWI in each level of the NNIS risk index were: index 0: 3.3%; index 1: 5.6%; index 2: 10.8%; index 3: 3.0%. The rates of SWI showed a good correlation with the NNIS risk index (gamma coefficient: 0.35 SE: 0.07). In addition, the index determined growing rates of SWI at each level of the traditional classification of operations (except in the contaminated ones), in the majority of the main operative procedures and among operations of abdominal and extraabdominal localizations.


CONCLUSIONS
The NNIS risk index is a better indicator of the intrinsic risk of patients than the traditional surgical wound classification alone.
Barrasa Villar
J I
JI
Unidad de Medicina Preventiva, Hospital de Calatayud, Zaragoza.
Domingo Cuevas
I
I
Vizmanos Sevilla
F
F
D000005:Abdomen / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D012307:Risk Factors; D013530:Surgical Wound Infection / Q000453:epidemiology* / Q000209:etiology; D013997:Time Factors