National Nosocomial Infection Surveillance Index Research Articles

Development and validation of baseline, perioperative and at-discharge predictive models for postsurgical prosthetic joint infection

ObjectivesTo develop and validate baseline, perioperative and at-discharge risk-scoring systems for postsurgical prosthetic joint infection (PJI) in patients undergoing arthroplasty. MethodsA multicentre prospective cohort study of patients undergoing hip and knee arthroplasty was performed. Patients were randomly assigned (2:1) to a derivation cohort (DC) or a validation cohort (VC). Multivariable predictive models of PJI were constructed at baseline (preoperative period), perioperative (adding perioperative variables) and at-discharge (adding wound state at discharge). The predictive ability of the models and scores was evaluated by area under the receiving operating characteristic curves (AUROC). ResultsThe DC and VC included 2324 and 1245 patients, respectively. Baseline model included total hip arthroplasty (THA), revision arthroplasty (RA), Charlson index and obesity. The AUROC for the score was 0.75 and 0.78 in the DC and VC, respectively. Perioperative model included THA, RA, obesity, National Nosocomial Infections Surveillance (NNIS) index ≥2, significant wound bleeding and superficial surgical site infection; the AUROC was 0.81 and 0.77 in the DC and VC, respectively. The at-discharge model included THA, RA, obesity, NNIS index ≥2, superficial surgical site infection and high-risk wound; the AUROC was 0.82 and 0.84 in the DC and VC, respectively. A score ≥8 points provided 99% negative predictive values for all models. ConclusionsSimple scores for predicting PJI at three different moments of care in patients undergoing arthroplasty were developed and validated. The scores allow early and accurate identification of high-risk individuals in whom enhanced preventive measures and follow-up may be needed. Further external validation is needed.

The development and validation of a novel model for predicting surgical complications in colorectal cancer of elderly patients: Results from 1008 cases

ObjectiveTo establish predicting models of surgical complications in elderly colorectal cancer patients. BackgroundSurgical complications are usually critical and lethal in the elderly patients. However, none of the current models are specifically designed to predict surgical complications in elderly colorectal cancer patients. MethodsDetails of 1008 cases of elderly colorectal cancer patients (age ≥ 65) were collected retrospectively from January 1998 to December 2013. Seventy-six clinicopathological variables which might affect postoperative complications in elderly patients were recorded. Multivariate stepwise logistic regression analysis was used to develop the risk model equations. The performance of the developed model was evaluated by measures of calibration (Hosmer-Lemeshow test) and discrimination (the area under the receiver-operator characteristic curve, AUC). ResultsThe AUC of our established Surgical Complication Score for Elderly Colorectal Cancer patients (SCSECC) model was 0.743 (sensitivity, 82.1%; specificity, 78.3%). There was no significant discrepancy between observed and predicted incidence rates of surgical complications (AUC, 0.820; P = .812). The Surgical Site Infection Score for Elderly Colorectal Cancer patients (SSISECC) model showed significantly better prediction power compared to the National Nosocomial Infections Surveillance index (NNIS) (AUC, 0.732; P ˂ 0.001) and Efficacy of Nosocomial Infection Control index (SENIC) (AUC; 0.686; P˂0.001) models. ConclusionsThe SCSECC and SSISECC models show good prediction power for postoperative surgical complication morbidity and surgical site infection in elderly colorectal cancer patients.

Early and late surgical site infections in ear surgery.

SUMMARYA retroauricular approach is routinely used for treating chronic otitis media. The incidence of surgical site infections after ear surgery is around 10% in contaminated or dirty procedures. This observational prospective study describes surgical site infections after chronic otitis media surgery with the retroauricular approach and investigated their potential predictive factors. This observational prospective study included patients suffering from chronic otitis media and eligible for therapeutic surgery with a retroauricular approach. During follow-up, surgical site infections were defined as "early" if occurring within 30 days after surgery or as "late" if occurring thereafter.The data of 102 patients were analysed. Concerning early surgical site infections, four cases were diagnosed (3.9%) and a significant association was found with preoperative antibiotic therapy, wet ear at pre-operative examination, class III (contaminated) in the surgical wound classification, NNIS (National Nosocomial Infection Surveillance) index > 1, and oral post-operative antibiotic use. Seven late surgical site infections were diagnosed (7.1%) between 90 and 160 days after surgery and were significantly correlated to otorrhoea during the 6 months before surgery, surgery duration ≤60 minutes, canal wall down technique and use of fibrin glue. Surgical site infections after chronic otitis media surgery seem to be associated with factors related to the inflammatory state of the middle ear at the time of surgery in early infections and with chronic inflammation in late infections.

Infección de la herida quirúrgica. Efectividad de los apósitos con polihexametileno biguanida

To analyze the effectiveness of a 0,2% polyhexamethylene biguanide dressing against the infection of a superficial surgical incision site (ISSIS) after a laparoscopic cholecystectomy. A randomized longitudinal single-blind study was conducted with two randomly assigned groups consisting of patients diagnosed with cholelithiasis soon to undergo an elective laparoscopic cholecystectomy. The dependent variable was ISSIS using the criteria of the Centre for Disease Control (CDC) (1999). The independent variables were the use of a 0,2% polyhexamethylene biguanide dressing (Group A), or a non occlusive dressing (Group B). The National Nosocomial Infections Surveillance (NNIS) index was used for assessing the risk of infection. The χ(2) test or Fisher test was used to evaluate the correlation between the independent variables. Of the total 197 cases, 96 (48.7%) were in group A and 101 (51.3%) in group B. No statistical differences were found between genders, duration of surgery (51.4 ± 21.2 vs 52.6 ± 23.4 minutes, in group A and B, respectively), or the NNIS index in either group. Six patients had an ISSIS (3.04%): 1 in group A (1.04%) and 5 in group B (4.95%), P=.212. The study was unable to correlate an ISSIS with the type of surgical dressing that was used, although it was not possible to rule out an association, as the study did not have sufficient statistical power.

Scoring system to predict the risk of surgical-site infection after colorectal resection2

There is no dedicated scoring system for predicting the risk of surgical-site infection (SSI) after resection of the colon or rectum. Generic scores, such as the National Nosocomial Infections Surveillance index, are not used by colorectal surgeons. Multivariable analysis of risk factors for SSI was performed in patients who underwent resection of the colon or rectum, and were followed during the first month after operation. A logistic regression model was used to identify determinant variables and construct a predictive score. There were 534 patients of whom 114 (21·3 per cent) developed SSI. In multivariable analysis, four parameters correlated with an increased risk of SSI: obesity (odds ratio (OR) 2·93, 95 per cent confidence interval 1·71 to 5·03), contamination class 3-4 (OR 3·33, 2·08 to 5·32), American Society of Anesthesiologists grade III-IV (OR 1·82, 1·14 to 2·90) and open surgery (OR 2·22, 1·01 to 4·88). Each of these contributed 1 point to the risk score. The observed risk of SSI was 5 per cent for a score of 0, 12·0 per cent for a score of 1 point, 18·7 per cent for 2 points, 44 per cent for 3 points and 68 per cent for 4 points. The area under the receiver operating characteristic curve for the score was 0·729. A simple clinical score based on four preoperative variables was clinically useful in predicting the risk of SSI in patients undergoing colorectal surgery.

Surgical site infection in patients submitted to orthopedic surgery: the NNIS risk index and risk prediction

The applicability of the risk index for surgical site infection of the National Nosocomial Infection Surveillance (NNIS) has been evaluated for its performance in different surgeries. In some procedures, it is necessary to include other variables to predict. to evaluate the applicability of the NNIS index for prediction of surgical site infection in orthopedic surgeries and to propose an alternative index. The study involved a historical cohort of 8236 patients who had been submitted to orthopaedic surgery. Statistical analysis was performed using multivariate logistic regression to fit the model. The incidence of infection was 1.41%. Prediction models were evaluated and compared to the NNIS index. The proposed model was not considered a good predictor of infection, despite moderately stratified orthopedic surgical patients in at least three of the four scores. The alternative model scored higher than the NNIS models in the prediction of infection.

Infección quirúrgica en un hospital de tercer nivel. Estudio de vigilancia prospectivo (2001–2004)

Introduction Surgical site infection (SSI) is a very common problem in hospital infection control. It represents a risk for the safety of the patient and therefore its reduction is a priority in Health Services. The aim of the study is to analyse the incidence of SSI in the surgical departments of a tertiary hospital. Material and methods A prospective cohort study was conducted on 14,455 patients admitted from January 2001 to December 2004. The cumulative incidence (CI) crude and adjusted for the National Nosocomial Infection Surveillance (NNIS) index and the incidence density (ID) of SSI were calculated. Results The CI of patients with SSI was 3.4% (95% CI: 3.0–3.7%), the CI of SSI was 3.5% and the observed ID was 0.28/100 surgical patients/day. Surgical units with the highest CI were maxillofacial (6%), gastrointestinal (5.3%) and cardiovascular (5.1%). Adjusting for length of stay, urology and paediatric surgery recorded the highest incidence rates, while ophthalmology and neurosurgery had the least. Colorectal surgery had the highest parameters (CI=10%; ID=0.57), followed by myocardial revascularisation and hip prosthesis. Among the surgical units and operative procedures assessed, the CI of SSI increased with the NNIS index. Conclusions The CI and ID of SSI observed in this study were similar to those obtained in previous European surveillance projects, and lower than those recorded in our hospital in 1994 which reflects a higher level of vigilance and a higher awareness in applying control measures.

Surgical site infection in a tertiary hospital. A prospective surveillance study (2001–2004)

IntroductionSurgical site infection (SSI) is a very common problem in hospital infection control. It represents a risk for the safety of the patient and therefore its reduction is a priority in Health Services. The aim of the study is to analyse the incidence of SSI in the surgical departments of a tertiary hospital. Material and methodsA prospective cohort study was conducted on 14,455 patients admitted from January 2001 to December 2004. The cumulative incidence (CI) crude and adjusted for the National Nosocomial Infection Surveillance (NNIS) index and the incidence density (ID) of SSI were calculated. ResultsThe CI of patients with SSI was 3.4% (95% CI: 3.0%–3.7%), the CI of SSI was 3.5% and the observed ID was 0.28/100 surgical patients/day. Surgical units with the highest CI were maxillofacial (6%), gastrointestinal (5.3%) and cardiovascular (5.1%). Adjusting for length of stay, urology and paediatric surgery recorded the highest incidence rates, while ophthalmology and neurosurgery had the least. Colorectal surgery had the highest parameters (CI=10%; ID=0.57), followed by myocardial revascularisation and hip prosthesis. Among the surgical units and operative procedures assessed, the CI of SSI increased with the NNIS index. ConclusionsThe CI and ID of SSI observed in this study were similar to those obtained in previous European surveillance projects, and lower than those recorded in our hospital in 1994 which reflects a higher level of vigilance and a higher awareness in applying control measures.

Surgical site infection surveillance and the predictive power of the National Nosocomial Infection Surveillance index as compared with alternative determinants in The Netherlands

<h3>Background</h3> Surgical site infection (SSI) surveillance typically includes comparison between observed and expected infection risks. Expected SSI numbers are usually derived from national data by use of the National Nosocomial Infection Surveillance (NNIS) index, developed by the Centers for Disease Control and Prevention. We aimed to estimate the predictive power of alternative SSI determinants to improve estimation of expected numbers. <h3>Methods</h3> We considered surveillance data comprising 93,511 surgical procedures, 3494 SSIs, and 11 putative determinants in The Netherlands in 1996 to 2004. Comparable procedures were pooled into 19 groups, and logistic regression backward elimination defined corresponding alternative models. The predictive power of the alternative models and the NNIS index were compared by testing the areas under the receiver operating characteristic curves. <h3>Results</h3> For 9 procedure groups, the alternative models predicted SSI better than the NNIS index (<i>P</i> < .05). However, the corresponding expected SSI numbers were marginally affected. <h3>Conclusion</h3> Our results do not support replacement of the NNIS index with procedure-specific determinants when comparing observed and expected SSI occurrence in feedback of surveillance results to hospitals.

Efecto de la vigilancia sobre la tasa de infección de la herida quirúrgica en prótesis de cadera y rodilla

To determine whether continuous surveillance of hospital-associated infections with regular feedback to the staff reduces the infection rate in orthopedic surgery. Prospective surveillance in two time periods in an orthopedic surgery department at a Spanish university hospital. Two infection control nurses and an epidemiologist surveyed all patients over a 3-year period for infections and potential risk factors. After an initial 24-month period (period A), surveillance for 12 months was conducted (period B). Between them adherence to recommendations was reinforced. A total of 1,088 patients were surveyed. In period A, 3.3% of all operations were followed by an infection, compared with 2.0% in period B (p = 0.14). Adherence to recommended schedule of surgical prophylaxis increased from 8.7% in the first year to 32.7% in the last year (p < 0,001). We also determined the NNIS (National Nosocomial Infections Surveillance) index risk in 383 patients, the NNIS index-risk 2 being more frequent in period A (16.8%) than in period B (5.4%) (p<0.001). Renal failure frequency was higher in period A (3.4% vs. 1.6%; p = 0.04). However, diabetes and neoplasms were the same in both periods. In period B, chronic obstructive pulmonary disease (COPD) (14.6 vs. 11.0; p = 0.05) and obesity (12.8 vs. 10.3; p = 0.12) predominated. The means for surgical intervention, hospital stay, and age, were very similar in both periods. Surveillance of hospital-associated infections including regular feedback to the staff is accompanied by a reduction in infection rates, possibly with lower cost and most patient safety. Therefore, such a surveillance program for orthopedic surgery department seems to be beneficial.

Applicability of the national nosocomial infections surveillance system risk index for the prediction of surgical site infections: a review

This review outlines the evolution of risk rates of surgical site infection adopted by the Study on the Efficacy of Nosocomial Infection Control (SENIC) and the National Nosocomial Infections Surveillance (NNIS) system, and evaluates their advantages and limitations. The types of surgical procedures for which the NNIS index has proven to be an efficient system for the classification of patients are presented. The necessity of adapting the NNIS index to take into account specific characteristics associated with hospitals and practices in various regions and countries is stressed. The requirement for further testing and development of the rate concerning specific procedures, particularly those involving orthopaedic surgery, is discussed.

Surgical site infection in patients submitted to digestive surgery: Risk prediction and the NNIS risk index

Some problems have been reported with the power of the National Nosocomial Infection Surveillance (NNIS) risk index to predict the risk of surgical site infections (SSI) for specific procedures. To develop an alternative risk prediction index for SSI and to compare the performance with the NNIS index. A prospective cohort study was carried out with all (609) patients submitted to digestive tract surgery in 2 general teaching hospitals in the city of São Paulo, Brazil, from August 2001 through March 2002. The final incidence rate of SSI was 24.5%; 149 cases of SSI were identified: 33 (22.1%) during hospitalization and 116 (77.9%) after discharge. Logistic multivariate analysis was used for construction of the model. Obesity, surgery risk, adjusted duration, and video laparoscopic surgery were statistically significant (P < .05) for all previous procedures. The performance of the NNIS model in this study showed a low predictive capacity for the occurrence of SSI as determined by the receiver operating characteristic (ROC) curve (0.627; 95% CI: 0.575-0.678) compared with the alternative model developed with this population (0.732; 95% CI: 0.685-0.779). The presence of obesity, adjusted duration, and surgery risk significantly increased the risk for SSI. The NNIS risk index was not significant for SSI in the sample studied, and laparoscopic access was associated with a significant reduction in the risk for SSI. Although the NNIS index is a well-known and simple index, other models depicting variables related to SSI with a better sensitivity and specificity can be developed. Additional studies are required to confirm our results.

Suitability of the NNIS index for estimating surgical-site infection risk at a small university hospital in Brazil.

To detect the occurrence of surgical-site infection (SSI) in our study sample, using the traditional variables of the National Nosocomial Infection Surveillance (NNIS) index with a locally modified cut-off point for the "T time" defining length of surgical procedure; to compare the modified and the traditional NNIS index under the hypothesis that a cut-off point discriminating procedures of short and long duration, based upon the actual experience of the study sample, can adequately predict the risk of SSI. A retrospective chart review of 9,322 patients undergoing surgical procedures in the period January 1993 to December 1998. SETING: A small university hospital (UH) in southern Brazil. The composite index using the local sample procedure-duration cut-off point (UH-index) performed better than any of the individual components of the composite index (anesthesia risk index and surgical-wound class [SWC]). The UH-index also predicted adequately the risk of SSI when compared to the traditional NNIS index, particularly when stratifying by SWC. A modified NNIS index, using the sample cut-off point, can adequately predict the risk of SSI in a given population. Further studies are needed to compare and validate the NNIS index of risk for populations other than those of the NNIS-participating hospitals. Larger samples using different hospitals with similar characteristics are needed to investigate the risk of SSI associated with specific operations.

Usefulness of intrinsic infection risk indexes as predictors of in-hospital death

Objective: Comparison of two measures of intrinsic infection risk for predicting in-hospital mortality risks among subjects and undergoing general surgery: the Study of the Efficacy of Nosocomial Infection Control (SENIC) index and the National Nosocomial Infection Surveillance (NNIS) index. Design: Prospective cohort study on 1483 patients admitted to the service of general surgery of a tertiary hospital. The main outcome measure was in-hospital death. Relative risks, crude and multiple-risk factor adjusted for by logistic regression analysis, and their 95% CIs were estimated. Results: During follow-up, 33 patients (2.2%) died. Both the SENIC and the NNIS indexes appeared related to in-hospital mortality risk in crude data. After several confounders (age, sex, severity of illness, American Society of Anethesiologists score, serum creatinine, serum albumin, stay at the intensive care unit, length of operation, type of surgical wound, and preoperative stay) were controlled for, the SENIC index showed a borderline significant trend with mortality ( p = 0.052), whereas the trend was significant for the NNIS index ( p = 0.026). The NNIS index also showed a linear trend with both crude and adjusted for (SENIC index) risk of death. The SENIC index did not exhibit any linear trend with adjusted for (NNIS index) risk of surgical wound infection. To delineate whether the SENIC index added explanatory information to the NNIS index (or vice versa), we regressed the SENIC index on the NNIS index (and vice versa) and computed a set of residuals for both indexes. In logistic regression analyses, the residuals of NNIS index added meaningful information to the SENIC index, whereas the residuals of the SENIC index did not add any relevant information to the NNIS index. These results remained unchanged after controlling for several confounders. Conclusions: Both the SENIC and the NNIS indexes are good predictors of in-hospital mortality risk. The NNIS index had greater capability for discriminating and predicting risk of death.

Nosocomial Infections in Surgical Patients: Comparison of Two Measures of Intrinsic Patient Risk

To compare, in subjects undergoing general surgery, two measures of intrinsic patients risk for nosocomial infection: the Study on the Efficacy of Nosocomial Infection Control (SENIC) index and the National Nosocomial Infection Surveillance (NNIS) System index.Prospective cohort study, with follow-up for 1 month after hospital discharge.The general surgery service of a tertiary hospital.Surgical-site infection.1,483 subjects aged 10 to 92 years.During follow-up, 155 patients developed nosocomial infection, yielding a cumulative incidence of 10.5%. The NNIS index showed a linear trend with both crude and adjusted (for SENIC index) rates of surgical-wound infection. The SENIC index did not exhibit any linear trend with adjusted (for NNIS index) rates of surgical-wound infection. To delineate whether the SENIC index added explanatory information to the NNIS index (or vice versa), we regressed each variable on the other. Logistic regression analyses confirmed the results of stratified analysis: residuals of the NNIS index added discriminating ability to the SENIC index, whereas residuals of the SENIC index did not improve the predictive power of the NNIS index.The NNIS index had a better ability than the SENIC index for discriminating and predicting risk of surgical-wound infection.