Risk-adjusted infection rates in surgery: a model for outcome measurement in hospitals developing new quality improvement programmes

Assessment of healthcare quality is a major challenge in countries such as Hungary where there is limited experience with measurement of patient outcomes. We sought to develop the capacity for valid outcome measurement in Hungarian hospitals using surgical site infection (SSI) surveillance as a model and to identify areas for improvement by comparing SSI rates in Hungarian hospitals to benchmarks published by the United States Centers for Disease Control and Prevention's National Nosocomial Infection Surveillance (NNIS) System. We surveyed the incidence of SSI among 5126 patients undergoing 6006 procedures in 20 public hospitals in Hungary during 1996 using the Hospitals in Europe Link for Infection Control through Surveillance (HELICS) protocol, a protocol consistent with the methods used by the NNIS System. Cholecystectomy, herniorrhaphy, appendectomy, and open reduction of fracture--four of the five most commonly performed procedures in Hungary in 1996--comprised 85% of the procedures analysed. Cumulative SSI rates for herniorrhaphy and appendectomy were comparable to NNIS System benchmarks. Cumulative SSI rates for cholecystectomy were significantly higher in Hungarian hospitals among risk categories that included open procedures. Nearly half of the hospitals had SSI rates for cholecystectomy that were high outliers (>90% percentile) compared to NNIS System benchmarks. Cumulative SSI rates for open reduction of fracture and mastectomy were significantly higher in Hungarian hospitals due to high rates in a few hospitals. The duration of surgery for all procedure types was substantially shorter in Hungarian hospitals compared with NNIS System hospitals. Future work should focus on optimizing prevention strategies for patients undergoing cholecystectomy, open reduction of fracture, and mastectomy. The effect of the utilization of open vs. laparoscopic cholecystectomy, short procedure duration, and procedure volume on SSI rates should be evaluated further. This programme expanded the capacity of Hungarian hospitals to perform surgical site infection surveillance and can serve as a model for hospitals in other countries with limited experience with outcome measurement.     

Performance of the national nosocomial infections surveillance risk index in predicting surgical site infection in australia.

BACKGROUND: The Victorian Hospital Acquired Infection Surveillance System (VICNISS) hospital-acquired infection surveillance system was established in 2002 in Victoria, Australia, and collates surgical site infection (SSI) surveillance data from public hospitals in Australia. OBJECTIVE: To evaluate the association between the US National Nosocomial Infections Surveillance (NNIS) system's risk index and SSI rates for 7 surgical procedures. METHODS: SSI surveillance was performed with NNIS definitions and methods for surgical procedures performed between November 2002 and September 2004. Correlations were assessed using the Goodman-Kruskal gamma statistic. RESULTS: Data were submitted for the following numbers of procedures: appendectomy, 545; coronary artery bypass graft (CABG), 4,632; cholecystectomy, 1,001; colon surgery, 623; cesarean section, 4,857; hip arthroplasty, 3,825; and knee arthroplasty, 2,416. NNIS risk index and increasing SSI rate were moderately well correlated for appendectomy ( gamma =0.55), colon surgery ( gamma =0.48), and cesarean section ( gamma =0.42). A fairly positive correlation was found for cholecystectomy ( gamma =0.17), hip arthroplasty ( gamma =0.2), and knee arthroplasty ( gamma =0.16). However, for CABG surgery, a poor association was found ( gamma =0.02). CONCLUSIONS: The NNIS risk index was positively correlated with an increasing SSI rate for all 7 procedures; the strongest correlation was found for appendectomy, cesarean section, and colon surgery, and the poorest correlation was found for CABG surgery. We believe that risk stratification with the NNIS risk index is appropriate for comparison of data for most procedures and superior to use of no risk adjustment. However, for some procedures, particularly CABG, further studies of alternative risk indexes are needed to better stratify patients.     

Procedure-specific surgical site infection rates and postdischarge surveillance in Scotland.

OBJECTIVE: To investigate the impact of postdischarge surveillance (PDS) on surgical-site infection (SSI) rates for selected surgical procedures in acute care hospitals in Scotland. DESIGN: Prospective surveillance of SSI after selected surgical procedures. SETTING: The Scottish Surveillance of Healthcare Associated Infection Programme (SSHAIP), which is based on the methodology of the Centers for Disease Control and Prevention (CDC) National Nosocomial Infections Surveillance system (NNIS). Thirty-two of 46 acute care hospitals throughout Scotland contributed data to SSHAIP for this study. METHODS: Data were from 21,710 operations that took place between April 1, 2002, and June 30, 2004; nine categories of surgical procedures were analyzed. CDC NNIS system definitions and methods were used for SSI PDS. PDS is a voluntary component of the mandatory SSI surveillance program in Scotland. PDS was categorized as none, passive, active without direct observation, and active with direct observation. RESULTS: From our study information, PDS data were available for 12,885 operations (59%). A total of 2,793 procedures (13%) were associated with passive PDS and 10,092 (46%) with active PDS. The SSI rate among the 8,825 operations with no PDS was 2.61% (95% confidence interval [CI], 2.3%-3.0%), which was significantly lower than the SSI rate found among the 12,885 operations for which PDS was performed (6.34% [95% CI, 5.9%-6.8%]). For breast surgery, cesarean section, hip replacement, and abdominal hysterectomy, the rate of SSI when PDS was performed was significantly higher than that when PDS was not performed (P<.01 for each procedure). No differences in SSI rates were found for surgery to repair fractured neck of the femur or for knee replacement. SSI rates were examined according to procedure type, performance of PDS, and NNIS risk index; rates of SSI increased with NNIS risk index within procedure group and PDS group. Logistic regression analyses confirmed that procedure type, performance of PDS, and NNIS risk index were all statistically independent predictors of report of an SSI (P<.05). CONCLUSIONS: This Scottish national data set incorporates a substantial amount of PDS data. We recommend a procedure-specific approach to PDS, with direct observation of patients after breast surgery, cesarean section, and hysterectomy, for which the length of stay is typically short. Readmission surveillance may be adequate to detect most SSIs after orthopedic surgery or vascular surgery, for which the length of stay is typically longer.     

Reduction of surgical site infection rates associated with active surveillance.

OBJECTIVE: To evaluate whether surgical site infection (SSI) rates decrease in surgical departments as a result of performing active SSI surveillance. DESIGN: Retrospective multiple logistic regression analyses. SETTING: A group of 130 surgical departments of German hospitals participating in the Krankenhaus Infektions Surveillance System (KISS). METHODS: Data for 19 categories of operative procedures performed between January 1997 and June 2004 were included (119,114 operations). Active SSI surveillance was performed according to National Nosocomial Infections Surveillance system (NNIS) methods and definitions. Departments' SSI rates were calculated individually for each year of surveillance and for each operative procedure category, taking into account when the individual departments had begun their surveillance activities. Multiple logistic regression analyses on a single operation basis were carried out with stepwise variable selection to predict outcomes for patients with SSI. The variables included were as follows: the department's year of participation, NNIS risk index variables, patients' age and sex, and the hospitals' structural characteristics, such as yearly operation frequency, number of beds, and academic status. RESULTS: For 14 of 19 operative procedure categories analyzed, there was a tendency toward lower SSI rates that was associated with increasing duration of SSI surveillance. In multiple logistic regression analyses of pooled data for all operative procedures, the departments' participation in the surveillance system was a significant independent protective factor. Compared with the surveillance year 1, the SSI risk decreased in year 2 (odds ratio, 0.84; 95% confidence interval, 0.77-0.93) and in year 3 (odds ratio, 0.75; 95% confidence interval, 0.68-0.82), and there was no change in year 4. CONCLUSION: The SSI incidence was reduced by one quarter as a result of the surveillance-induced infection control efforts, which indicates the usefulness of a voluntary surveillance system.     

Surveillance for surgical site infection after hospital discharge: a surgical procedure-specific perspective.

OBJECTIVE: To estimate the rate of surgical site infection (SSI) occurring after hospital discharge, to evaluate whether limiting surveillance to inpatients underestimates the true rate of SSI, and to select surgical procedures that should be included in a postdischarge surveillance program. DESIGN: Prospective surveillance study. SETTING: A surgical ward at a university teaching hospital in Italy. PATIENTS: A total of 264 surgical patients were included in the study. RESULTS: The global SSI rate was 10.6% (28 patients); 17 (60.2%) of patients with an SSI developed the infection after hospital discharge. The overall mean length of postoperative stay (+/-SD) for patients who acquired a postdischarge SSI was 4.9+/-3.7 days, and SSI was diagnosed a mean duration (+/-SD) of 11.5+/-4.5 days after surgery. Among procedures with postdischarge SSIs, those classified by the National Nosocomial Infections Surveillance system (NNIS) as herniorrhaphy, mastectomy, other endocrine system, and other integumentary system were associated with a mean postoperative stay that was less than the mean time between the operation and the onset of SSI. Four (36%) of in-hospital SSIs occurred after procedures with an NNIS risk index of 0, and 7 (64%) occurred after procedures with an NNIS risk index of 1 or higher. Of the 17 SSIs diagnosed after discharge, 14 procedures (82%) had an NNIS risk index of 0, compared with 3 procedures (18%) with an NNIS risk index of 1 or higher. CONCLUSIONS: Our results revealed an increased risk of postdischarge SSI after some types of surgical procedures and suggest that there is an important need to change from generalized to NNIS operative category-directed postdischarge surveillance, at least for procedures locally considered to be high-risk.     

Infections after coronary artery bypass graft surgery in Victorian hospitals--VICNISS Hospital Acquired Infection Surveillance

OBJECTIVE: To establish a surveillance program reporting surgical site infection rates after coronary artery bypass graft surgery (CABGS) in Victorian public hospitals. METHODS: The VICNISS Coordinating Centre was established in 2002 to implement and co-ordinate a standardised surveillance system for hospital-acquired infections in acute care Victorian public hospitals. Using validated definitions and methodology from the Centers for Disease Control and Prevention's National Nosocomial Infection Surveillance (NNIS) program, data on risk-adjusted surgical site infection (SSI) rates were collected and submitted to the Coordinating Centre for collation and reporting. RESULTS: Six large Melbourne metropolitan hospitals contributed data for CABGS for the period 11 November 2002 to 30 June 2004, comprising a total of 3,482 patient records. Of 3,398 complete records, the aggregate SSI rates per 100 procedures for NNIS risk category 1 and 2 were 4.4 (95% Cl 3.7-5.3) and 6.0 (95% Cl 4.5-7.8) respectively. The deep sternal SSI rates were 0.6 (95% Cl 0.4-1.3) and 0.5 (95% Cl 0.5-2.4 for patients in risk category 1 and 2 respectively. The most common pathogen identified was Staphylococcus aureus. CONCLUSION: This early data from VICNISS demonstrates similar CABGS SSI rates to those reported by NNIS in the USA, but higher than reported by the German Nosocomial Infection Surveillance System. IMPLICATIONS: The adoption of a statewide, co-ordinated surveillance program using validated internationally accepted methodologies allows hospitals to benchmark their infection rates against aggregate local and international data and to examine infection prevention interventions.     

Finding a method for optimizing risk adjustment when comparing surgical-site infection rates.

OBJECTIVE: To investigate whether stratification of the risk of developing a surgical-site infection (SSI) is improved when a logistic regression model is used to weight the risk factors for each procedure category individually instead of the modified NNIS System risk index. DESIGN AND SETTING: The German Nosocomial Infection Surveillance System, based on NNIS System methodology, has 273 acute care surgical departments participating voluntarily. Data on 9 procedure categories were included (214,271 operations). METHODS: For each of the procedure categories, the significant risk factors from the available data (NNIS System risk index variables of ASA score, wound class, duration of operation, and endoscope use, as well as gender and age) were identified by multiple logistic regression analyses with stepwise variable selection. The area under the receiver operating characteristic (ROC) curve resulting from these analyses was used to evaluate the predictive power of logistic regression models. RESULTS: For most procedures, at least two of the three variables contributing to the NNIS System risk index were shown to be independent risk factors (appendectomy, knee arthroscopy, cholecystectomy, colon surgery, herniorrhaphy, hip prosthesis, knee prosthesis, and vascular surgery). The predictive power of logistic regression models (including age and gender, when appropriate) was low (between 0.55 and 0.71) and for most procedures only slightly better than that of the NNIS System risk index. CONCLUSION: Without the inclusion of additional procedure-specific variables, logistic regression models do not improve the comparison of SSI rates from various hospitals.     

Nosocomial infections in heart surgery patients: active surveillance in two Italian hospitals

In Italy no nosocomial infection surveillance database has been established despite the fact that a decrease of nosocomial infection rates was one of the priorities of the Italian National Health Plan 1998--2000. Heart surgery operations are the most frequent high risk procedures in western countries. Active surveillance was performed at the heart surgery wards of two Italian hospitals (Rome and Catania, Southern Italy) in accordance with the methods described for the National Nosocomial Infections Surveillance (NNIS) System of the USA. In both hospitals surgical site infections (SSIs) were the most frequently encountered type of nosocomial infections, accounting for 57.2% in Rome and 50% in Catania, and SSI rates in coronary artery bypass grafts with both chest and donor site incisions, calculated by risk index equal to 1, were above the 90th percentile for the NNIS System. The urinary catheter-associated urinary tract infection (UTI) rate (5.8%) in Catania exceeded the 90th percentile for the NNIS System, while the device-associated UTI (1.6%), bloodstream (4.1%) and pneumonia (8.0%) rates, from the hospital in Rome, did not. All device utilization ratios were lower than the 10th percentile for the NNIS System. Our study demonstrated that the NNIS methodology is applicable to Italian hospitals, although with some limitations mainly regarding the minimal surveillance duration required for significant interhospital comparison, and highlighted the need of a national comparison of surveillance data as benchmark.     

Improved risk adjustment for comparison of surgical site infection rates.

OBJECTIVE: To develop prognostic models for improved risk adjustment in surgical site infection surveillance for 5 surgical procedures and to compare these models with the National Nosocomial Infection Surveillance system (NNIS) risk index. DESIGN: In a multicenter cohort study, prospective assessment of surgical site infection and risk factors was performed from 1996 to 2000. In addition, risk factors abstracted from patient files, available in a national medical register, were used. The c-index was used to measure the ability of procedure-specific logistic regression models to predict surgical site infection and to compare these models with models based on the NNIS risk index. A c-index of 0.5 indicates no predictive power, and 1.0 indicates perfect predictive power. SETTING: Sixty-two acute care hospitals in the Dutch national surveillance network for nosocomial infections. PARTICIPANTS: Patients who underwent 1 of 5 procedures for which the predictive ability of the NNIS risk index was moderate: reconstruction of the aorta (n=875), femoropopliteal or femorotibial bypass (n=641), colectomy (n=1,142), primary total hip prosthesis (n=13,770), and cesarean section (n=2,962). RESULTS: The predictive power of the new model versus the NNIS index was 0.75 versus 0.62 for reconstruction of the aorta (P<.01), 0.78 versus 0.58 for femoropopliteal or femorotibial bypass (P<.001), 0.69 versus 0.62 for colectomy (P<.001), 0.64 versus 0.56 for primary total hip prosthesis arthroplasty (P<.001), and 0.70 versus 0.54 for cesarean section (P<.001). CONCLUSION: Data available from hospital information systems can be used to develop models that are better at predicting the risk of surgical site infection than the NNIS risk index. Additional data collection may be indicated for certain procedures--for example, total hip prosthesis arthroplasty.     

Does stratifying surgical site infection rates by the National Nosocomial Infection Surveillance risk index influence the rank order of the hospitals in a surveillance system?

We performed a study to investigate whether stratification of surgical site infection (SSI) rates according to the National Nosocomial Infection Surveillance (NNIS) risk index could lead to a better basis for comparison of surgical units compared with simpler methods. A retrospective analysis of surveillance data of the German national nosocomial infection surveillance system (KISS, Krankenhaus Infektions Surveillance System) was completed with data from 234 volunteer surgical departments. In all, 4275 SSIs of 223 367 operations from 12 surgical procedure categories were surveyed over a 66 month period from January 2001 to June 2006. Active SSI surveillance was performed according to the NNIS method and Centers for Disease Control and Prevention definitions. For each department, two SSI rates were calculated per procedure: the crude infection rate (CIR) and the risk-adjusted standardised infection ratio (SIR) based on the NNIS risk index. Ranking was performed for the departments using both rates. The correlation between the two ranking positions was investigated by Spearman's correlation coefficient (P). For all 12 operative procedure categories, there was a strong correlation between the CIR and the SIR (P>0.95). A department's rank position does not change remarkably when the CIR, which is easier to understand and simpler to record, is taken into account for comparison instead of the SIR.     

Duration of operation as a risk factor for surgical site infection: comparison of English and US data

T times are used to categorize surgical procedures into long and short durations. They constitute a part of the US National Nosocomial Infection Surveillance (NNIS) risk index that is widely used internationally in surveillance for surgical site infections (SSIs). The objective of this study was to compare the US NNIS T times with data collected in England. The Surgical Site Infection Surveillance Service in England holds data collected by 168 hospitals in 13 categories of surgical procedures between 1997 and 2002. The 75(th) percentile and corresponding T time were calculated from English data and compared with US times. Differences in rates of SSI above and below the T times were compared. Graphical methods were used to assess the cut points that exhibited an association with risk of SSI. The results show that English and US T times were the same for all surgical categories except coronary artery bypass graft and vascular surgery, where the English T time was 4 h. The 75(th) percentile time for hip hemiarthroplasties was 40 min less than for total hip replacements (THR). Although the incidence of SSI in THR was significantly higher in operations lasting for longer than the T time (P<0.05), no association between risk of SSI and T times set at 1, 1.5 or 2 h was observed for hip hemiarthroplasties. In conclusion, operations lasting for longer than the T time were associated with a higher risk of SSI in most categories. In the hip prosthesis category, this association only applied to THR.     

The standardized incidence ratio as a reliable tool for surgical site infection surveillance.

OBJECTIVE: To evaluate whether the standardized incidence ratio (SIR) is a more reliable tool for comparing rates and temporal trends of surgical site infection (SSI) in surgery wards than the incidence rate among patients with an National Nosocomial Infections Surveillance system (NNIS) risk index category of 0. DESIGN: Observational, prospective cohort study in a sequential SSI surveillance system. SETTING: Volunteer surgery wards in a surveillance network in northern France that annually conducted SSI surveillance for 3 months from 1998 to 2000. METHODS: The incidence rate was the number of SSIs divided by the number of patients included, stratified by the NNIS risk index category. SIR was the observed number of SSIs divided by the expected number computed using a multiple regression model. RESULTS: Overall, 26,904 patients in 67 surgery wards were enrolled. Between 1998 and 2000, the SSI incidence rate among patients with NNIS risk index category 0 decreased from 2.1% to 1.4%, which was a 33% reduction (P=.002). The SIR decreased from 1.2 (95% confidence interval [CI], 1.1-1.3) to 0.8 (95% CI, 0.7-0.9), which was a 20% decrease per year and an overall 33% reduction. The number of SSIs was significantly higher than expected in 17 of 201 surveillance periods over the 3 years. The classification of the wards according to the 2 indicators over the 3 years showed that wards with a high SIR did not consistently have the highest SSI incidence rate among patients with NNIS risk index category 0, partly because the type of surgical procedure and the duration of follow-up are not taken into account in the NNIS risk index. CONCLUSION: SIR should be considered a reliable indicator to estimate the reduction in SSI incidence that results from implementation of infection control policies and for comparison of SSI rates between wards.     

Surveillance of hospital-acquired infections in Australia--One Nation, Many States

Surveillance programmes for hospital-acquired infections differ amongst the Australian states. Victoria, New South Wales, Queensland and South Australia have recent substantial initiatives in development of statewide programmes. Whilst the definitions for surgical site infections (SSIs) and bloodstream infections (BSI) developed by the Australian Infection Control Association (AICA) do not differ from the US National Nosocomial Infection Surveillance (NNIS) programme definitions for SSI and intensive care unit (ICU) acquired central line-associated BSI, only two states use NNIS risk adjustment methods in reporting infection rates. Differences exist in the surgical procedures under surveillance, ICU surveillance, hospital-wide BSI surveillance, staff health immunization surveillance, process measures such us surgical antibiotic prophylaxis and small hospital programmes. Only in the area of antibiotic use surveillance has national consensus been reached. In Victoria, NNIS risk adjustment had limited usefulness in predicting SSIs, especially after coronary artery bypass graft (CABG) surgery. Ventilator-associated pneumonia (VAP) surveillance had limited acceptance, and is not undertaken in other states. Regular reporting of surgical antibiotic prophylaxis data has been followed by improvement in choice of antibiotic in some procedures. The South Australian programme for the surveillance of multiresistant organisms (MROs) has documented substantial improvement in meticillin-resistant Staphylococcus aureus (MRSA) morbidity over time coincident with the introduction of hand hygiene programmes and other measures. In Queensland, statewide monitoring of needlestick injuries is established. In Victoria, the small hospital programme concentrated on process measures, and in Queensland with a standardized investigation pathways for "signal" events. Data quality presented substantial challenges in small Victorian hospitals. Whilst state-based programmes have facilitated communication between hospitals and their coordinating centre, Australia still lacks national coordination and a national database on hospital infections. The differing approaches of the states illustrate many of the fundamental questions facing hospital infection surveillance today.     

Risk stratification for surgical site infections in Australia: evaluation of the US National Nosocomial Infection Surveillance risk index

This study evaluated the US National Nosocomial Infection Surveillance (NNIS) risk index (RI) in Australia for different surgical site infection (SSI) outcomes (overall, in-hospital, post-discharge, deep-incisional and superficial-incisional infection) and investigated local risk factors for SSI. A SSI surveillance dataset containing 43 611 records for 13 common surgical procedures, conducted in 23 hospitals between February 2001 and June 2005, was used for the analysis. The NNIS RI was evaluated against the observed SSI data using diagnostic test evaluation statistics (sensitivity, specificity, positive predictive value, negative predictive value). Sensitivity was low for all SSI outcomes (ranging from 0.47 to 0.69 and from 0.09 to 0.20 using RI thresholds of 1 and 2 respectively), while specificity varied depending on the RI threshold (0.55 and 0.93 with thresholds of 1 and 2 respectively). Mixed-effects logistic regression models were developed for the five SSI outcomes using a range of available potential risk factors. American Society of Anaesthesiologists (ASA) physical status score >2, duration of surgery, absence of antibiotic prophylaxis and type of surgical procedure were significant risk factors for one or more SSI outcomes, and risk factors varied for different SSI outcomes. The discriminatory ability of the NNIS RI was insufficient for its use as an accurate risk stratification tool for SSI surveillance in Australia and its sensitivity was too low for it to be appropriately used as a prognostic indicator.     

Standardized infection ratios for three general surgery procedures: a comparison between Spanish hospitals and U.S. centers participating in the National Nosocomial Infections Surveillance System.

OBJECTIVES: To compare Spanish surgical wound infection (SWI) rates for three procedures with those published by the U.S. NNIS System, and to analyze quarterly trends. DESIGN: This was a 4-year prospective analysis of SWI using data from a Spanish nosocomial infection surveillance network based on CDC classification criteria. SWI rates were computed as standardized infection ratios (SIRs). Trends for both SWIs and SIRs were evaluated by linear regression. SETTING: Forty-three Spanish hospitals during 1997 through 2000. PATIENTS: Those undergoing cholecystectomy (n = 7,631), appendectomy (n = 5,780), and herniorrhaphy (n = 9,864). RESULTS: For cholecystectomy patients, the SWI rate was 4.38% and the SIR was 3.32. Both of these variables showed a slightly rising, although nonsignificant, linear trend during the study period. For appendectomy patients, the SWI rate was 7.94% and the SIR was 2.86. The linear trend was increasing for both, but only the SWI rate attained significance. For herniorrhaphy patients, the SWI rate was 1.77% and the SIR was 1.64. Both of these variables showed a significant descending tendency during the 4 years. CONCLUSIONS: Because the SIR takes into account the patient risk category, it is the best indicator of the trend shown by the SWI rate over time for a given surgical procedure. According to our comparison of SIRs with reference NNIS System values, SWI rates for cholecystectomy and appendectomy were high. Monitoring of the SIR will provide a basis for the design of infection control measures and the assessment of their effectiveness.     

Impact of a six-year control programme on surgical site infections in France: results of the INCISO surveillance

Surgical site infections (SSI) are a key target of nosocomial infection control policy. We evaluated the impact of a six-year surveillance system based on data from INCISO, a network of volunteer surgical wards from hospitals in Northern France. Each year surgical patients were enrolled consecutively and surveyed during their in- and out-hospital stay until 30 days following surgery. A standardised form was completed for each patient including SSI diagnosis according to standard criteria and several risk factors such as wound class, American Society of Anesthesiologists score, operation duration, elective/emergency, videoscopy and type of surgery. A dashboard was displayed at the end of each annual survey, so that participants could compare with other surgery adjusted for National Nosocomial Infections Surveillance system (NNIS) risk index and standardised incidence ratio (SIR). Over the six years, 3661 SSI were identified in 150 440 surgical patients (crude incidence: 2.4%) from 548 surgery wards. The crude SSI incidence decreased from 3.8 to 1.7% (P for trend <0.0001, relative reduction: -55%) and the NNIS-0 adjusted SSI incidence from 2.0 to 1% (P for trend <0.0001; relative reduction: -50%). An active surveillance system striving for benchmark through a network is an effective strategy to reduce SSI incidence. Sustaining control efforts have to be made to maintain low SSI level beyond the three primer years.     

Reduced risk of surgical site infections through surveillance in a network.

OBJECTIVE: To estimate the effect of multicentre surveillance for nosocomial infections on patients' risk of surgical site infection (SSI). DESIGN: Prospective multi-centre cohort study, from January 1996 to December 2000. SETTING: Acute care hospitals in The Netherlands. STUDY PARTICIPANTS: All 50 hospitals performing surveillance for one of seven selected procedures in the Dutch surveillance network for nosocomial infections PREZIES were invited. Thirty-seven hospitals participated (74%) and provided information on 21 920 operations, after which 885 (4%) SSI occurred. INTERVENTIONS: The surveillance comprised the following: Development of surveillance methodology by multidisciplinary team; use of a standardized registration protocol and software; regular training of data collectors; anonymous inter-hospital comparison of infection rates and feedback of results; appointment of one contact person per hospital, responsible for data collection; and dissemination of results to other health care professionals. Regular discussion of both successful and failing prevention strategies that had been instituted based on the surveillance results. OUTCOME MEASURE: Risk of SSI. RESULTS: The risk of infection was reduced for patients who had an operation during the fourth surveillance year (RR = 0.69; 95% confidence interval (CI) = 0.52-0.89) and decreased further for patients operated on during the fifth surveillance year (RR = 0.43; CI = 0.24-0.76) as compared with patients who underwent surgery within one year of the start of surveillance in their hospital. No significant risk reduction was observed for patients operated on during the second and third surveillance years. CONCLUSION: Surveillance, supported by participation in a surveillance network, reduced the risk of SSI in surgical patients registered in the Dutch surveillance network PREZIES. Our results suggest that infection control teams need to be perseverant and that surveillance programmes should be given time before evaluation.     

Impact of postdischarge surveillance on surgical-site infection rates for coronary artery bypass procedures.

OBJECTIVE: To assess the influence of postdischarge infection surveillance on risk-adjusted surgical-site infection rates for coronary artery bypass graft (CABG) procedures. DESIGN: Prospective surveillance of surgical-site infections after CABG. SETTING: Tertiary-care referral hospital. METHODS: Data on surgical-site infections were collected for 1,324 CABG procedures during 27 months. They were risk adjusted and analyzed according to the surgical surveillance protocol of the National Nosocomial Infections Surveillance (NNIS) System of the Centers for Disease Control and Prevention, with and without postdischarge data. RESULTS: Data were available for 96% of the patients. Of the 88 surgical-site infections, 28% were identified prior to discharge and 72% postdischarge. More chest than harvest-site infections were identified (46% vs 11%) prior to discharge, and more harvest-site than chest infections were identified in the outpatient setting (42% vs 14%). The surgical-site infection rate for patients stratified under risk index 1, calculated without postdischarge surveillance, was 2.9%; when compared with that of the NNIS System, the P value was .29. When postdischarge surveillance was included, the surgical-site infection rate was 4.9% and statistically significant when compared with that of the NNIS System (P = .007). For patients stratified under risk index 2, the rates with and without postdischarge surveillance were 11.7% and 10.0%, respectively; when compared with the NNIS System rates, the P values were .000008 and .0006, respectively. CONCLUSIONS: Only 28% of the surgical-site infections would have been detected if surveillance had been limited to hospital stay. Postdischarge surveillance identified more surgical-site infections among risk index 1 patients. Hospitals with comprehensive postdischarge surveillance after CABG procedures are likely to record higher surgical-site infection rates than those that do not perform such surveillance .     

Impact of surgeon-specific feedback on surgical site infection rates in Thailand

Data on surgeon-specific feedback on surgical site infection (SSI) rates are not currently available in Thailand. The authors conducted a before and after study among patients undergoing surgery in seven Thai hospitals to examine whether a feedback system to surgeons could reduce SSI rates. After a six-month surveillance period, surgeons were provided with their own SSI rates and standardized infection ratios (SIRs). The criteria of the National Nosocomial Infection Surveillance (NNIS) system were used to determine SSI rates, and the SSI rates were compared with the NNIS report in terms of the SIR. To compare the SIR before and after intervention, the SIR ratio was calculated and logistic regression analysis was used to estimate the relative impact of surgeon-specific feedback, adjusting for patient sex, patient age, degree of wound contamination, American Society of Anesthesiologists' score, duration of operation, type of operation, use and duration of antibiotic prophylaxis, and length of pre-operative stay. After confidential feedback to surgeons for six months, SSI rates and the SIR remained unchanged. The SSI rate in the pre-intervention period was 1.7 infections/100 operations and the corresponding SIR was 0.8 [95% confidence intervals (CI)=0.6-0.9]. In the post-intervention period, the SSI rate was 1.8 infections/100 operations, with a corresponding SIR of 0.8 (95%CI=0.7-0.9). The SIR ratio was 1.0. The relative risk of SSI after surgeon-specific feedback suggested that this intervention had no effect (adjusted relative risk=1.02, 95%CI=0.77-1.35). Feedback to surgeons on their SSI rates did not reduce the rates of such infections in Thailand.     

Active surveillance of nosocomial infections in heart surgery patients: implementation of the American National Nosocomial Infections Surveillance (NNIS) System in a large hospital in Rome

The authors present the implementation of the American NNIS System method for active surveillance in the heart surgery and its intensive care unit (ICU) of a large hospital in Rome (almost 1.000 beds). This surveillance was based on full time infection control professionals. Device-associated infection rates were calculated for adult ICU surveillance component. For surgical patient surveillance component we used the surgical site infection (SSI) risk index based on wound class, duration of operation and American Society of Anesthesiology score. The NNIS System method allowed us to understand the most relevant problems in heart surgery patients: in comparison with NNIS data, we found high rates of SSIs both in procedures on valves and in coronary artery bypass grafts. The central line-associated bloodstream infection rate was higher than the American median rate. Therefore, we decided to focus on surgical risk factors linked to SSIs and to revise recommendations for intravascular-device use. In conclusion, in our experience the NNIS System method proved to be a very useful and versatile tool for nosocomial infections active surveillance.