Improved risk adjustment for comparison of surgical site infection rates

Challenges of Modeling Outcomes for Surgical Infections: A Word of Caution

Background: We developed a novel analytic tool for colorectal deep organ/space surgical site infections (C-OSI) prediction utilizing both institutional and extra-institutional American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP) data. Methods: Elective colorectal resections (2006-2014) were included. The primary end point was C-OSI rate. A Bayesian-Probit regression model with multiple imputation (BPMI) via Dirichlet process handled missing data. The baseline model for comparison was a multivariable logistic regression model (generalized linear model; GLM) with indicator parameters for missing data and stepwise variable selection. Out-of-sample performance was evaluated with receiver operating characteristic (ROC) analysis of 10-fold cross-validated samples. Results: Among 2,376 resections, C-OSI rate was 4.6% (n = 108). The BPMI model identified (n = 57; 56% sensitivity) of these patients, when set at a threshold leading to 80% specificity (approximately a 20% false alarm rate). The BPMI model produced an area under the curve (AUC) = 0.78 via 10-fold cross- validation demonstrating high predictive accuracy. In contrast, the traditional GLM approach produced an AUC = 0.71 and a corresponding sensitivity of 0.47 at 80% specificity, both of which were statstically significant differences. In addition, when the model was built utilizing extra-institutional data via inclusion of all (non-Mayo Clinic) patients in ACS-NSQIP, C-OSI prediction was less accurate with AUC = 0.74 and sensitivity of 0.47 (i.e., a 19% relative performance decrease) when applied to patients at our institution. Conclusions: Although the statistical methodology associated with the BPMI model provides advantages over conventional handling of missing data, the tool should be built with data specific to the individual institution to optimize performance.

Early prediction model of organ/space surgical site infection after elective gastrointestinal or hepatopancreatobiliary cancer surgery

BACKGROUND

Organ/space SSI is a significant clinical problem. However, early detection of organ/space SSI is difficult, and previous predictive models are limited in their prognostic ability. We aimed to develop and validate a prediction model of organ/space surgical site infection (SSI) using postoperative day 3 laboratory data in patients who underwent gastrointestinal or hepatopancreatobiliary cancer resection.

METHODS

This retrospective cohort study using a single-center hospital data from April 2013 to September 2017 included all adult patients who underwent elective gastrointestinal or hepatopancreatobiliary cancer resection. The primary outcome was a presence of organ/space SSI including anastomotic leakage, pancreatic fistula, biliary fistula, or intra-abdominal abscess. We developed and validated a logistic regression model to predict organ/space SSI using laboratory data on postoperative day (POD) 3. Similar models using laboratory data on POD 1 or 5 were developed to compare the predictive ability of each model.

RESULTS

A total of 1578 patients were included. Organ/space SSI was diagnosed in 107 patients, with median diagnosis days of 6 (interquartile range, 4-9 days) after surgery. A prediction model using five commonly measured variables on POD 3 was created with the area under the curve (AUC) of 0.883 (95%CI 0.819-0.946). The AUC of a model with POD 1 laboratory data was 0.751 (95%CI 0.655-0.848), while that of POD 5 laboratory data was 0.818 (95%CI 0.730-0.906).

CONCLUSIONS

Laboratory data on POD 3 could forecast organ/space SSI precisely. Further prospective studies are warranted to investigate the clinical impact of this model.

Outcomes are Local: Patient, Disease, and Procedure-Specific Risk Factors for Colorectal Surgical Site Infections from a Single Institution

BACKGROUND

Colorectal surgical site infections (SSIs) contribute to postoperative morbidity, mortality, and resource utilization. Risk factors associated with colorectal SSI are well-documented. However, quality improvement efforts are informed by national data, which may not identify institution-specific risk factors.

METHOD

Retrospective cohort study of colorectal surgery patients uses institutional ACS-NSQIP data from 2006 through 2014. ACS-NSQIP data were enhanced with additional variables from medical records. Multivariable logistic regression identified factors associated with SSI development.

RESULTS

Of 2376 patients, 213 (9.0%) developed at least one SSI (superficial 4.8%, deep 1.1%, organ space 3.5%). Age < 40, BMI > 30, ASA3+, steroid use, smoking, diabetes, pre-operative sepsis, higher wound class, elevated WBC or serum glutamic-oxalocetic transaminase, low hematocrit or albumin, Crohn's disease, and prolonged incision-to-closure time were associated with increased SSI rate (all P < 0.01). After adjustment, BMI > 30, steroids, diabetes, and wound contamination were associated with SSI. Patients with Crohn's had greater odds of SSI than other indications.

CONCLUSION

Institutional modeling of SSI suggests that many previously suggested risk factors established on a national level do not contribute to SSIs at our institution. Identification of institution-specific predictors of SSI, rather than relying upon conclusions derived from external data, is a critical endeavor in facilitating quality improvement and maximizing value of quality investments.

Patients at High-Risk for Surgical Site Infection

BACKGROUND

Surgical site infections (SSIs) are a significant healthcare quality issue, resulting in increased morbidity, disability, length of stay, resource utilization, and costs. Identification of high-risk patients may improve pre-operative counseling, inform resource utilization, and allow modifications in peri-operative management to optimize outcomes.

METHODS

Review of the pertinent English-language literature.

RESULTS

High-risk surgical patients may be identified on the basis of individual risk factors or combinations of factors. In particular, statistical models and risk calculators may be useful in predicting infectious risks, both in general and for SSIs. These models differ in the number of variables; inclusion of pre-operative, intra-operative, or post-operative variables; ease of calculation; and specificity for particular procedures. Furthermore, the models differ in their accuracy in stratifying risk. Biomarkers may be a promising way to identify patients at high risk of infectious complications.

CONCLUSIONS

Although multiple strategies exist for identifying surgical patients at high risk for SSIs, no one strategy is superior for all patients. Further efforts are necessary to determine if risk stratification in combination with risk modification can reduce SSIs in these patient populations.

Clinical relevance and effect of surgical wound classification in appendicitis: Retrospective evaluation of wound classification discrepancies between surgeons, Swissnoso-trained infection control nurse, and histology as well as surgical site infection rates by wound class

BACKGROUND

Surgical wound classification (SWC) is used for risk stratification of surgical site infection (SSI) and serves as the basis for measuring quality of care. The objective was to examine the accuracy and reliability of SWC. This study was purposed to evaluate the discrepancies in SWC as assessed by three groups: surgeons, an infection control nurse, and histopathologic evaluation. The secondary aim was to compare the risk-stratified SSI rates using the different SWC methods for 30 d postoperatively.

METHODS

An analysis was performed of the appendectomies from January 2013 to June 2014 in the Cantonal Hospital of Schaffhausen. SWC was assigned by the operating surgeon at the end of the procedure and retrospectively reviewed by a Swissnoso-trained infection control nurse after reading the operative and pathology report. The level of agreement among the three different SWC assessment groups was determined using kappa statistic. SSI rates were analyzed using a chi-square test.

RESULTS

In 246 evaluated cases, the kappa scores for interrater reliability among the SWC assessments across the three groups ranged from 0.05 to 0.2 signifying slight agreement between the groups. SSIs were more frequently associated with trained infection control nurse-assigned SWC than with surgeons based SWC.

CONCLUSIONS

Our study demonstrated a considerable discordance in the SWC assessments performed by the three groups. Unfortunately, the currently practiced SWC system suffers from ambiguity in definition and/or implementation of these definitions is not clearly stated. This lack of reliability is problematic and may lead to inappropriate comparisons within and between hospitals and surgeons.

Systematic review of risk prediction scores for surgical site infection or periprosthetic joint infection following joint arthroplasty

Accurate identification of individuals at high risk of surgical site infections (SSIs) or periprosthetic joint infections (PJIs) influences clinical decisions and development of preventive strategies. We aimed to determine progress in the development and validation of risk prediction models for SSI or PJI using a systematic review. We searched for studies that have developed or validated a risk prediction tool for SSI or PJI following joint replacement in MEDLINE, EMBASE, Web of Science and Cochrane databases; trial registers and reference lists of studies up to September 2016. Nine studies describing 16 risk scores for SSI or PJI were identified. The number of component variables in a risk score ranged from 4 to 45. The C-index ranged from 0·56 to 0·74, with only three risk scores reporting a discriminative ability of >0·70. Five risk scores were validated internally. The National Healthcare Safety Network SSIs risk models for hip and knee arthroplasties (HPRO and KPRO) were the only scores to be externally validated. Except for HPRO which shows some promise for use in a clinical setting (based on predictive performance and external validation), none of the identified risk scores can be considered ready for use. Further research is urgently warranted within the field.

Preoperative risk prediction of surgical site infection requiring hospitalization or reoperation in patients undergoing vascular surgery

OBJECTIVE

The objective of this study was to develop a surgical site infection (SSI) prediction score for risk assessment before elective vascular surgery.

METHODS

We conducted a nested case-control study among patients who underwent elective vascular (abdominal aortic and peripheral arterial) surgery from January 1, 2003, to December 31, 2007, at Mayo Clinic (Rochester, Minn) an academic tertiary surgical center. Cases were patients with SSI requiring hospitalization; controls (one or two per case) were matched on type of procedure and date of surgery. Clinical data were collected by chart review. A risk score based on preoperative variables was developed using multivariable logistic regression and bootstrap resampling. The C statistic, equivalent to the area under the receiver operating characteristic curve, was used to assess discrimination. Calibration was assessed by plotting percentile risk groups of model-predicted values against observed proportions of subjects with SSI.

RESULTS

Eighty-four cases were compared with 160 controls. Preoperative variables independently associated with SSI risk were critical limb ischemia, previous SSI, prior revascularization procedure, and chronic obstructive pulmonary disease. A prediction model containing these variables was developed (model and risk score C statistic of 0.737 and 0.727, respectively). The calibration curve did not appear to deviate appreciably from the 45-degree line of identity.

CONCLUSIONS

We developed an SSI risk score based on noninvasive preoperative variables with acceptable discrimination and calibration. This tool needs prospective and external validation.

The Development of Statistical Models for Predicting Surgical Site Infections in Japan: Toward a Statistical Model–Based Standardized Infection Ratio

OBJECTIVE

To develop and internally validate a surgical site infection (SSI) prediction model for Japan.

DESIGN

Retrospective observational cohort study.

METHODS

We analyzed surveillance data submitted to the Japan Nosocomial Infections Surveillance system for patients who had undergone target surgical procedures from January 1, 2010, through December 31, 2012. Logistic regression analyses were used to develop statistical models for predicting SSIs. An SSI prediction model was constructed for each of the procedure categories by statistically selecting the appropriate risk factors from among the collected surveillance data and determining their optimal categorization. Standard bootstrapping techniques were applied to assess potential overfitting. The C-index was used to compare the predictive performances of the new statistical models with those of models based on conventional risk index variables.

RESULTS

The study sample comprised 349,987 cases from 428 participant hospitals throughout Japan, and the overall SSI incidence was 7.0%. The C-indices of the new statistical models were significantly higher than those of the conventional risk index models in 21 (67.7%) of the 31 procedure categories (P<.05). No significant overfitting was detected.

CONCLUSIONS

Japan-specific SSI prediction models were shown to generally have higher accuracy than conventional risk index models. These new models may have applications in assessing hospital performance and identifying high-risk patients in specific procedure categories.

Infect. Control Hosp. Epidemiol. 2016;37(3):260–271

Depicting the interplay between organisational tiers in the use of a national quality registry to develop quality of care in Sweden

Background

With a pending need to identify potential means to improved quality of care, national quality registries (NQRs) are identified as a promising route. Yet, there is limited evidence with regards to what hinders and facilitates the NQR innovation, what signifies the contexts in which NQRs are applied and drive quality improvement. Supposedly, barriers and facilitators to NQR-driven quality improvement may be found in the healthcare context, in the politico-administrative context, as well as with an NQR itself. In this study, we investigated the potential variation with regards to if and how an NQR was applied by decision-makers and users in regions and clinical settings. The aim was to depict the interplay between the clinical and the politico-administrative tiers in the use of NQRs to develop quality of care, examining an established registry on stroke care as a case study.

Methods

We interviewed 44 individuals representing the clinical and the politico-administrative settings of 4 out of 21 regions strategically chosen for including stroke units representing a variety of outcomes in the NQR on stroke (Riksstroke) and a variety of settings. The transcribed interviews were analysed by applying The Consolidated Framework for Implementation Research (CFIR).

Results

In two regions, decision-makers and/or administrators had initiated healthcare process projects for stroke, engaging the health professionals in the local stroke units who contributed with, for example, local data from Riksstroke. The Riksstroke data was used for identifying improvement issues, for setting goals, and asserting that the stroke units achieved an equivalent standard of care and a certain level of quality of stroke care. Meanwhile, one region had more recently initiated such a project and the fourth region had no similar collaboration across tiers. Apart from these projects, there was limited joint communication across tiers and none that included all individuals and functions engaged in quality improvement with regards to stroke care.

Conclusions

If NQRs are to provide for quality improvement and learning opportunities, advances must be made in the links between the structures and processes across all organisational tiers, including decision-makers, administrators and health professionals engaged in a particular healthcare process.

Electronic supplementary material

The online version of this article (doi:10.1186/s12913-015-1188-2) contains supplementary material, which is available to authorized users.

A multifaceted prevention program to reduce infection after cesarean section: Interventions assessed using an intensive postdischarge surveillance system

BACKGROUND

We assessed the effects of the components of a multifaceted and evidence-based caesarean-section surgical site infection (SSI) prevention program on the SSI rate after cesarean section using a postdischarge surveillance (PDS) system.

METHODS

Multiple prevention interventions were serially implemented. SSI case finding was undertaken through active inpatient surveillance and intensive PDS using a standardized form at the 6-week postdischarge visit. SSI diagnosis was made using the Centers for Disease Control and Prevention standardized criteria. All cesarean deliveries between July 2007 and December 2012 were included. Changes in SSI rate were analyzed using segmented regression analysis.

RESULTS

Nine thousand four hundred forty-two cesarean sections were assessed during the study period. PDS forms were completed for 7,985 women (85%). SSI was detected in 451 cases (5.6%): 91% were superficial, 9% were deep/organ-space infections. The SSI rate decreased incrementally from 8.2% at baseline to 4.1%; significant decreases were observed after optimizing antibiotic prophylaxis timing, using a surgical safety checklist, and enhancing prenatal education to discourage prehospital self-removal of hair. Nonelective surgeries or those undertaken after >12 hours of rupture of membranes had a significantly higher rate compared with those without either risk factor (6.3% vs 3.2%; P < .001).

CONCLUSIONS

A multifaceted SSI prevention strategy, with periodic feedback of data, led to a significant reduction in SSI rates after cesarean section.

Surgical site infection risk factors and risk stratification

Preoperative identification of the risk factors for surgical site infection and patient risk stratification are essential for deciding whether surgery is appropriate, educating patients on their individual risk of complications, and managing postoperative expectations. Early identification of these factors is also necessary to help guide both patient medical optimization and perioperative care planning. Several resources are currently available to track and analyze healthcare-associated infections, including the Centers for Disease Control and Prevention's National Healthcare Safety Network. In addition, the Centers for Disease Control and Prevention and the American Academy of Orthopaedic Surgeons are exploring collaborative opportunities for the codevelopment of a hip and/or knee arthroplasty national quality measure for periprosthetic joint infection.

Validation of a Modified Version of the National Nosocomial Infections Surveillance System Risk Index for Health Services Research

Objective.

To validate the National Nosocomial Infections Surveillance system risk index through administrative data to predict surgical site infections.

Design.

Retrospective cohort study.

Setting.

Population-based analysis in Ontario, Canada.

Patients.

All elderly patients who underwent elective surgery from April 1, 1992, through March 31, 2006 (n = 469,349).

Methods.

Data on procedural and patient outcomes were gathered from linked population-wide hospital discharge records and physician claims. The 75th percentile of surgical duration was estimated through anesthesiologist billing fees recorded in 15-minute increments; the American Society of Anesthesiology score of at least 3 out of 5 was estimated by diagnostic codes for severe systemic illness; and all surgeries were classified as clean or clean-contaminated because of their elective nature (thus, the maximum score on the modified index was 2).

Results.

A total of 147,216 surgeries (31%) had a score of 0;246,592 (53%) had a score of 1; and 75,541 (16%) had a score of 2 on the modified index. The 30-day risk of surgical site infection increased with each increment in the modified index (score of 0, 5.4%; score of 1, 8.0%; score of 2, 14.3%; P < .001). The association was evident for surgical site infection diagnosed during the index admission (score of 0, 2.0%; score of 1, 3.7%; score of 2, 8.9%; P < .001), as well as that associated with reoperation or death (score of 0, 0.04%; score of 1, 0.23%; score of 2, 0.73%; P < .001). The modified index predicted increases in surgical site infection risk within each of 11 surgical subgroups. In accord with past research, the modified index had modest discrimination (C statistic, 0.59), and the majority of surgical site infections (72%) occurred within lower risk strata.

Conclusions.

The modified index predicts surgical site infection in population-based analyses and is associated with incremental increases in risk.

Improving Risk-Adjusted Measures of Surgical Site Infection for the National Healthcare Safely Network

Background.

The National Healthcare Safety Network (NHSN) has provided simple risk adjustment of surgical site infection (SSI) rates to participating hospitals to facilitate quality improvement activities; improved risk models were developed and evaluated.

Methods.

Data reported to the NHSN for all operative procedures performed from January 1, 2006, through December 31, 2008, were analyzed. Only SSIs related to the primary incision site were included. A common set of patient- and hospital-specific variables were evaluated as potential SSI risk factors by univariate analysis. Some ific variables were available for inclusion. Stepwise logistic regression was used to develop the specific risk models by procedure category. Bootstrap resampling was used to validate the models, and the c-index was used to compare the predictive power of new procedure-specific risk models with that of the models with the NHSN risk index as the only variable (NHSN risk index model).

Results.

From January 1, 2006, through December 31, 2008, 847 hospitals in 43 states reported a total of 849,659 procedures and 16,147 primary incisional SSIs (risk, 1.90%) among 39 operative procedure categories. Overall, the median c-index of the new procedure-specific risk was greater (0.67 [range, 0.59–0.85]) than the median c-index of the NHSN risk index models (0.60 [range, 0.51–0.77]); for 33 of 39 procedures, the new procedure-specific models yielded a higher c-index than did the NHSN risk index models.

Conclusions.

A set of new risk models developed using existing data elements collected through the NHSN improves predictive performance, compared with the traditional NHSN risk index stratification.

Complex Surgical Site Infections and the Devilish Details of Risk Adjustment: Important Implications for Public Reporting

Objective.

To validate the National Nosocomial Infection Surveillance (NNIS) risk index as a tool to account for differences in case mix when reporting rates of complex surgical site infection (SSI).

Design.

Prospective cohort study.

Setting.

Twenty-four community hospitals in the southeastern United States.

Methods.

We identified surgical procedures performed between January 1, 2005, and June 30, 2007. The Goodman-Kruskal gamma or G statistic was used to determine the correlation between the NNIS risk index score and the rates of complex SSI (not including superficial incisional SSI). Procedure-specific analyses were performed for SSI after abdominal hysterectomy, cardiothoracic procedures, colon procedures, insertion of a hip prosthesis, insertion of a knee prosthesis, and vascular procedures.

Results.

A total of 2,257 SSIs were identified during the study period (overall rate, 1.19 SSIs per 100 procedures), of which 1,093 (48.4%) were complex (0.58 complex SSIs per 100 procedures). There were 45 complex SSIs identified following 7,032 abdominal hysterectomies (rate, 0.64 SSIs per 100 procedures); 63 following 5,318 cardiothoracic procedures (1.18 SSIs per 100 procedures); 139 following 5,144 colon procedures (2.70 SSIs per 100 procedures); 63 following 6,639 hip prosthesis insertions (0.94 SSIs per 100 procedures); 73 following 9,658 knee prosthesis insertions (0.76 SSIs per 100 procedures); and 55 following 6,575 vascular procedures (0.84 SSIs per 100 procedures). All 6 procedure-specific rates of complex SSI were significantly correlated with increasing NNIS risk index score (P< .05).

Conclusions.

Some experts recommend reporting rates of complex SSI to overcome the widely acknowledged detection bias associated with superficial incisional infection. Furthermore, it is necessary to compensate for case-mix differences in patient populations, to ensure that intrahospital comparisons are meaningful. Our results indicate that the NNIS risk index is a reasonable method for the risk stratification of complex SSIs for several commonly performed procedures.

Should National Standards for Reporting Surgical Site Infections Distinguish between Primary and Revision Orthopedic Surgeries?

Objective.

To compare the surgical site infection (SSI) rate after primary total hip arthroplasty with the SSI rate after revision total hip arthroplasty.

Design.

Retrospective cohort study.

Setting.

Mayo Clinic in Rochester, Minnesota, a referral orthopedic center.

Patients.

All patients undergoing primary total hip arthroplasty or revision total hip arthroplasty during the period from January 1, 2002, through December 31, 2006.

Methods.

We obtained data on total hip arthroplasties from a prospectively maintained institutional surgical database. We reviewed data on SSIs collected prospectively as part of routine infection control surveillance, using the criteria of the Centers for Disease Control and Prevention for the definition of an SSI. We used logistic regression analyses to evaluate differences between the SSI rate after primary total hip arthroplasty and the SSI rate after revision total hip arthroplasty.

Results.

A total of 5,696 total hip arthroplasties (with type 1 wound classification) were analyzed, of which 1,381 (24%) were revisions. A total of 61 SSIs occurred, resulting in an overall SSI rate of 1.1% for all total hip arthroplasties. When stratified by the National Nosocomial Infection Surveillance (NNIS) risk index, SSI rates were 0.5%, 1.2%, and 1.6% in risk categories 0, 1, and 2, respectively. After controlling for the NNIS risk index, the risk of SSI after revision total hip arthroplasty was twice as high as that after primary total hip arthroplasty (odds ratio, 2.2 [95% confidence interval, 1.3-3.7]). In the analysis restricted to the development of deep incisional or organ space infections, the risk of SSI after revision total hip arthroplasty was nearly 4 times that after primary total hip arthroplasty (odds ratio, 3.9 [95% confidence interval, 2.0-7.6]).

Conclusion.

Including revision surgeries in the calculation of SSI rates can result in higher infection rates for institutions that perform a larger number of revisions. Taking NNIS risk indices into account does not eliminate this effect. Differences between primary and revision surgeries should be considered in national standards for the reporting of SSIs.

Surgical site infection: the principles and practice of surveillance: Part 2: analysing and interpreting data

In Part 1 of this two-part series on surveillance of surgical site infection (SSI) the principles of surveillance methodology and the role of surveillance in reducing the risk of infection were discussed. This second part focuses on the analysis and interpretation SSI surveillance data, the challenges this presents and of some of the solutions. The risk of SSI is conventionally expressed as the percentage of operations that develop SSI. However, this metric is strongly dependant on the length of post-operative stay, since infections take several days to become apparent and are difficult to identify after discharge. Comparisons based on more severe infections detected in inpatients or those readmitted with SSI are more likely to provide reliable data for inter-hospital comparisons. The precision of the estimated rates and adjustment for intrinsic risk factors are important considerations, although ultimately mechanisms for discriminating significantly higher rates merely indicate a problem requiring further investigation rather than definitive evidence of poor practice.

Risk factors for surgical site infection in breast surgery

AIMS AND OBJECTIVES

To study risks of surgical site infection in breast surgery. The objectives were to measure the association of postoperative infection with patient- and procedure-related factors.

BACKGROUND

The infection rate in breast surgery is expected to be low but it varies a lot. The variation is recommended to be assessed by measuring procedure-related factors.

DESIGN

A retrospective chart review of 982 breast surgery patients was completed.

METHODS

The data on patient demographics, procedure types, patient and surgery-related factors were collected. A multivariate logistic regression model for all breast operations (n=982), lumpectomies (n=700) and mastectomies (n=282) was performed.

RESULTS

The infection rate was 6.7%. In a multivariate logistic regression model for all operations, a contaminated or dirty wound, high American Society of Anesthesiologists score, high body mass index, use of surgical drains and re-operation predicted increased infection risk. In lumpectomies high body mass index and use of surgical drains predicted increased risk. In mastectomies, the significant predictor was re-operation.

CONCLUSIONS

The surgical site infection rate was high. In addition to the two classical risks (high wound class and anaesthesia risk), high body mass index, re-operation and use of surgical drain increased the infection risk among all patients.

RELEVANCE TO CLINICAL PRACTICE

In breast surgery careful assessment, documentation and adherence to aseptic practices are important with all patients. Patients with heavy weight need special attention. The need for antimicrobial prophylaxis in re-operations and the need of surgical drains in lumpectomies are important to consider carefully.

Risk factors associated with surgical site infections following vascular surgery at a German university hospital

Surgical site infection (SSI) after vascular surgery is a serious complication increasing morbidity, mortality, and costs for healthcare systems. A 4-year retrospective cohort study was performed in a university hospital with patients who had undergone arterial vascular surgery below the aortic arch. Investigated variables included demographics and clinical data. Forty-four of 756 patients experienced SSI, 29 of which were superficial, five were deep, and 10 had organ/space infections. Coagulase-negative staphylococci (22%), enterococci (20%), and Staphylococcus aureus (18%) were the most common pathogens. Independent risk factors for SSIs were femoral grafting [odds ratio (OR) 6·7], peripheral atherosclerotic disease, Fontaine stages III–IV (OR 4·1), postoperative drainage >5 days (OR 3·6), immunosuppression (OR 2·8), duration of operation >214 min (OR 2·8), and body mass index >29 (OR 2·6). The application of perioperative antibiotic prophylaxis was an independent protective factor (OR 0·2). Patients with certain risk factors for SSIs warrant special attention for infection prevention.

The Mayo prosthetic joint infection risk score: implication for surgical site infection reporting and risk stratification

OBJECTIVE

The goal of this study was to develop a prognostic scoring system for the development of prosthetic joint infection (PJI) that could risk-stratify patients undergoing total hip (THA) or total knee (TKA) arthroplasties.

DESIGN

Previously reported case-control study.

SETTING

Tertiary referral care setting from 2001 through 2006.

METHODS

A derivation data set of 339 cases and 339 controls was used to develop 2 scores. A baseline score and a 1-month-postsurgery risk score were computed as a function of the relative contributions of risk factors for each model. Points were assigned for the presence of each factor and then summed to get a subject's risk score.

RESULTS

The following risk factors were detected from multivariable modeling and incorporated into the baseline Mayo PJI risk score: body mass index, prior other operation on the index joint, prior arthroplasty, immunosuppression, ASA score, and procedure duration (c index, 0.722). The 1-month-postsurgery risk score contained the same variables in addition to postoperative wound drainage (c index, 0.716).

CONCLUSION

The baseline score might help with risk stratification in relation to public reporting and reimbursement as well as targeted prevention strategies in patients undergoing THA or TKA. The application of the 1-month-postsurgery PJI risk score to patients undergoing THA or TKA might benefit those undergoing workup for PJI.

Pediatric surgical site infection in the developing world: a Kenyan experience

BACKGROUND

The purpose of the current study was to determine the incidence of pediatric surgical site infections(SSIs) at an academic children’s hospital in rural sub-Saharan Africa and to identify potentially modifiable risk factors.

METHODS

Prospectively collected data from 1,008 surgical admissions to Bethany Kids Kijabe Hospital (Kijabe, Kenya) were analyzed retrospectively. Follow-up data were available in 940 subjects.

RESULTS

SSIs occurred in 6.8% of included subjects(N = 64). Superficial (69%) and deep (29%) infections of the back (38%) and head (25%) were most common. When comparing children who developed SSI to those who did not, we found that wound contamination classification and duration of operation were the only variables with significant differences between groups.

CONCLUSIONS

Our rate of SSI among pediatric patients insub-Saharan Africa is the lowest reported in the literature to date. More work is needed to identify modifiable risk factors for pediatric SSI in low- and middle-income countries.

Improved risk adjustment in public reporting: coronary artery bypass graft surgical site infections

OBJECTIVE

The objective was to develop a new National Healthcare Safety Network (NHSN) risk model for sternal, deep incisional, and organ/space (complex) surgical site infections (SSIs) following coronary artery bypass graft (CABG) procedures, detected on admission and readmission, consistent with public reporting requirements.

PATIENTS AND SETTING

A total of 133,503 CABG procedures with 4,008 associated complex SSIs reported by 293 NHSN hospitals in the United States.

METHODS

CABG procedures performed from January 1, 2006, through December 31, 2008, were analyzed. Potential SSI risk factors were identified by univariate analysis. Multivariate analysis with forward stepwise logistic regression modeling was used to develop the new model. The c-index was used to compare the predictive power of the new and NHSN risk index models.

RESULTS

Multivariate analysis independent risk factors included ASA score, procedure duration, female gender, age, and medical school affiliation. The new risk model has significantly improved predictive performance over the NHSN risk index (c-index, 0.62 and 0.56, respectively).

CONCLUSIONS

Traditionally, the NHSN surveillance system has used a risk index to provide procedure-specific risk-stratified SSI rates to hospitals. A new CABG sternal, complex SSI risk model developed by multivariate analysis has improved predictive performance over the traditional NHSN risk index and is being considered for endorsement as a measure for public reporting.

Development and validation of a novel stratification tool for identifying cancer patients at increased risk of surgical site infection

OBJECTIVE

To identify cancer-specific predictors of postoperative surgical site infection (SSI), and to develop a risk-stratification prognostic tool and compare its performance with traditional measures.

BACKGROUND

The incidence and risk factors for SSI in cancer patients are unknown; current risk-stratification tools are not cancer-specific.

METHODS

A prospective cohort study of patients undergoing elective operations (n = 503) at a tertiary cancer center was conducted. SSI was assessed using postdischarge active surveillance. Multivariate logistic regression analyses were performed to identify predictors of SSI, and β-coefficients were used to create a scoring system. The sum of these was used to create a Risk of Surgical Site Infection in Cancer (RSSIC) score. The RSSIC was validated using bootstrapping techniques, and its discrimination was compared with the National Nosocomial Infection Surveillance (NNIS) risk index.

RESULTS

The 30-day SSI incidence was 24%. Significant predictors of SSI included preoperative chemotherapy (OR = 1.94 [95% CI, 1.16-3.25]), clean-contaminated wounds (OR = 2.1 [95% CI, 1.24-3.55]), operative time ≥2 hours (OR = 1.75 [95% CI, 1.01-3.04]) and ≥4 hours (OR = 2.24 [95% CI, 1.22-4.1]), and surgical site: groin (OR = 4.65 [95% CI, 1.69-12.83]), and head/neck (OR = 0.12 [95% CI, 0.02-0.89]). The RSSIC score stratified patients into 4 risk strata for SSI. The performance of this score exceeded that of the NNIS score (AUC = 0.70 vs. 0.63, respectively; P = 0.01).

CONCLUSION

SSIs are common following cancer surgery. Preoperative chemotherapy, in addition to other common risk factors, was identified as a significant predictor for SSI in cancer patients. The RSSIC improves risk-stratification of cancer patients and identifies those that may benefit from more aggressive or novel preventive strategies.

Performance, revision, and extension of the National Nosocomial Infections Surveillance system's risk index in Brazilian hospitals

OBJECTIVE

To assess the benefit of using procedure-specific alternative cutoff points for National Nosocomial Infections Surveillance (NNIS) risk index variables and of extending surgical site infection (SSI) risk prediction models with a postdischarge surveillance indicator.

DESIGN

Open, retrospective, validation cohort study.

SETTING

Five private, nonuniversity Brazilian hospitals.

PATIENTS

Consecutive inpatients operated on between January 1993 and May 2006 (other operations of the genitourinary system [n = 20,723], integumentary system [n = 12,408], or musculoskeletal system [n = 15,714] and abdominal hysterectomy [n = 11,847]).

METHODS

For each procedure category, development and validation samples were defined nonrandomly. In the development samples, alternative SSI prognostic scores were constructed using logistic regression: (i) alternative NNIS scores used NNIS risk index covariates and cutoff points but locally derived SSI risk strata and rates, (ii) revised scores used procedure-specific alternative cutoff points, and (iii) extended scores expanded revised scores with a postdischarge surveillance indicator. Performances were compared in the validation samples using calibration, discrimination, and overall performance measures.

RESULTS

The NNIS risk index showed low discrimination, inadequate calibration, and predictions with high variability. The most consistent advantage of alternative NNIS scores was regarding calibration (prevalence and dispersion components). Revised scores performed slightly better than the NNIS risk index for most procedures and measures, mainly in calibration. Extended scores clearly performed better than the NNIS risk index, irrespective of the measure or operative procedure.

CONCLUSIONS

Locally derived SSI risk strata and rates improved the NNIS risk index's calibration. Alternative cutoff points further improved the specification of the intrinsic SSI risk component. Controlling for incomplete postdischarge SSI surveillance provided consistently more accurate SSI risk adjustment.

Thromboprophylaxis, bleeding and post-operative prosthetic joint infection in total hip and knee arthroplasty: a comprehensive literature review

INTRODUCTION

Concerns regarding risk versus benefit, that is, the possible impact of surgical-site bleeding on post-operative joint infections, have contributed to a continuing debate over recommendations for venous thromboembolism (VTE) prophylaxis in post-surgical orthopedic patients undergoing total hip and knee arthroplasty (THA/TKA).

AREAS COVERED

A comprehensive literature search using MEDLINE covering the period 2004-2009 was conducted, and published studies that focused on THA and TKA and contained data applicable to thromboprophylaxis, post-surgical wound infection and bleeding are reviewed in this paper. The search strategy included various combinations of terms related to lower limb joint arthroplasty, anticoagulant drugs, post-operative bleeding and prosthetic joint infection (wound infection). Methodological constraints included failure in some studies to define an infection, variations among the studies in the definitions of bleeding and differences in the follow-up time for capturing infection and bleeding events. Despite this, this comprehensive review identified observational, 'real-world' data that can contribute in important ways to the existing evidence base.

EXPERT OPINION

There are insufficient data to either confirm or refute the hypothesis that post-operative bleeding is a mediating pathophysiologic factor linking pharmacologic VTE prophylaxis to an increased risk for wound infection. Studies specifically designed to examine the interrelationship between thromboprophylaxis, bleeding and wound infections following THA/TKA are warranted.

Infection after primary hip arthroplasty: a comparison of 3 Norwegian health registers

BACKGROUND AND PURPOSE

The aim of the present study was to assess incidence of and risk factors for infection after hip arthroplasty in data from 3 national health registries. We investigated differences in risk patterns between surgical site infection (SSI) and revision due to infection after primary total hip arthroplasty (THA) and hemiarthroplasty (HA).

MATERIALS AND METHODS

This observational study was based on prospective data from 2005-2009 on primary THAs and HAs from the Norwegian Arthroplasty Register (NAR), the Norwegian Hip Fracture Register (NHFR), and the Norwegian Surveillance System for Healthcare-Associated Infections (NOIS). The Norwegian Patient Register (NPR) was used for evaluation of case reporting. Cox regression analyses were performed with revision due to infection as endpoint for data from the NAR and the NHFR, and with SSI as the endpoint for data from the NOIS.

RESULTS

The 1-year incidence of SSI in the NOIS was 3.0% after THA (167/5,540) and 7.3% after HA (103/1,416). The 1-year incidence of revision due to infection was 0.7% for THAs in the NAR (182/24,512) and 1.5% for HAs in the NHFR (128/8,262). Risk factors for SSI after THA were advanced age, ASA class higher than 2, and short duration of surgery. For THA, the risk factors for revision due to infection were male sex, advanced age, ASA class higher than 1, emergency surgery, uncemented fixation, and a National Nosocomial Infection Surveillance (NNIS) risk index of 2 or more. For HAs inserted after fracture, age less than 60 and short duration of surgery were risk factors of revision due to infection.

INTERPRETATION

The incidences of SSI and revision due to infection after primary hip replacements in Norway are similar to those in other countries. There may be differences in risk pattern between SSI and revision due to infection after arthroplasty. The risk patterns for revision due to infection appear to be different for HA and THA.

"But my patients are different!": risk adjustment in 2012 and beyond

Feedback of surgical site infection (SSI) rates to surgeons improves patient outcomes and should be considered a cornerstone of any infection control program. For as long as feedback of SSI data has occurred, those in infection control have often heard a searing retort from indignant surgeons: “But my patients are different!”

Fortunately, epidemiologists have several tools to use in response. One of the most commonly used approaches involves risk adjustment for differences in case mix between the group of interest (eg, a surgeon's patients) and a comparator. In other words, risk adjustment levels the playing field.

Formal risk adjustment for rates of SSI has existed for almost 50 years but is still an imperfect science. In fact, risk adjustment for different variables can lead to different conclusions. Over the past 2 decades, the National Healthcare Safety Network (NHSN) risk index has been used by many hospitals to perform risk adjustment for rates of SSI. The NHSN risk index is simple and effective but has undergone considerable scrutiny. Numerous investigators have described scenarios and/or procedures for which the risk index performed poorly and have offered suggestions for improvement. Indeed, Robert Gaynes summarized some of the shortcomings of the NHSN risk index in 2 editorials 10 years ago, stating, “A composite risk index that captures the joint influence of [intrinsic patient risk] and other risk factors is required before meaningful comparisons of SSI rates can be made by surgeons, among institutions, or across time.”

Prolonged duration of operation: an indicator of complicated surgery or of surgical (mis)management?

PURPOSE

The aim of this study was to investigate whether a prolonged operative time should be regarded as an indicator of quality problems in operating rooms or as patient-specific risk factors when analyzing surgical site infection (SSI) rates.

METHOD

Data from the SSI component of the German national nosocomial infection surveillance system (KISS) were used to address this question. Eight procedure categories tracked by at least 30 departments participating in KISS were included in the analysis, namely, hip (2 types) and knee prosthesis, breast surgery, hernia repair, C-section, cholecystectomy and colon operations. Various multiple logistic regression analyses were performed for each procedure category to predict duration of operation. Patient factors (sex, age, American Society of Anesthesiologists score, wound contamination class) and hospital factors (hospital status, size, annual volume) were considered. The area under the receiver operating characteristic (ROC) curve was used to evaluate predictive power including patient- and hospital-based factors.

RESULTS

A total of 253,454 operations were included in the analysis. In general, the predictive power of the model including all variables for the different procedure types was relatively low (C-index range: 0.57-0.63) and not much higher than that of the models including only patient-based or only hospital-based variables, respectively. The predictive power for the duration of operative time based on the model including only hospital-based variables was as good as or better than that of the model including only patient-based factors.

CONCLUSION

Duration of operation is at least partially determined by hospital factors and, consequently, should be used as a quality indicator to compare SSI infections between hospitals, rather than being used as a patient factor to adjust comparisons between hospitals.

Cluster-randomized, crossover trial of the efficacy of plain soap and water versus alcohol-based rub for surgical hand preparation in a rural hospital in Kenya

Background

The aim of this cluster-randomized, crossover trial was to compare the efficacy of plain soap and water with an alcohol-based handrub for surgical hand preparation and prevention of surgical-site infection (SSI) in a Kenyan rural hospital.

Methods

A total of 3317 patients undergoing clean and clean-contaminated surgery were included. Follow-up data 30 days after discharge were available for 3133 patients (94·5 per cent).

Results

SSI occurred in 255 patients (8·1 per cent), with similar rates for both study arms: 8·3 per cent for alcohol-based handrub versus 8·0 per cent for plain soap and water (odds ratio 1·03, 95 per cent confidence interval 0·80 to 1·33). After adjustment for imbalances between study arms and clustering effects, the main outcome measure remained unchanged (adjusted odds ratio 1·06, 0·81 to 1·38). The duration of surgery and wound contamination class independently predicted SSI. The cost difference between the methods was small (€4·60 per week for alcohol-based handrub compared with €3·30 for soap and water).

Conclusion

There was no statistically or clinically significant difference in SSI rates, probably because more important factors contribute to SSI development. However, this study demonstrated the feasibility and affordability of alcohol-based handrubs for hand preparation before surgery in settings without continuous, clean water. Registration number: NCT00987402 (http://www.clinicaltrials.gov).

Developing a risk stratification model for surgical site infection after abdominal hysterectomy

OBJECTIVE

The incidence of surgical site infection (SSI) after hysterectomy ranges widely from 2% to 21%. A specific risk stratification index could help to predict more accurately the risk of incisional SSI following abdominal hysterectomy and would help determine the reasons for the wide range of reported SSI rates in individual studies. To increase our understanding of the risk factors needed to build a specific risk stratification index, we performed a retrospective multihospital analysis of risk factors for SSI after abdominal hysterectomy.

METHODS

Retrospective case-control study of 545 abdominal and 275 vaginal hysterectomies from July 1, 2003, to June 30, 2005, at 4 institutions. SSIs were defined by using Centers for Disease Control and Prevention/National Nosocomial Infections Surveillance criteria. Independent risk factors for abdominal hysterectomy were identified by using logistic regression.

RESULTS

There were 13 deep incisional, 53 superficial incisional, and 18 organ-space SSIs after abdominal hysterectomy and 14 organ-space SSIs after vaginal hysterectomy. Because risk factors for organ-space SSI were different according to univariate analysis, we focused further analyses on incisional SSI after abdominal hysterectomy. The maximum serum glucose level within 5 days after operation was highest in patients with deep incisional SSI, lower in patients with superficial incisional SSI, and lowest in uninfected patients (median, 189, 156, and 141 mg/dL, respectively; P = .005). Independent risk factors for incisional SSI included blood transfusion (odds ratio [OR], 2.4) and morbid obesity (body mass index [BMI], >35; OR, 5.7). Duration of operation greater than the 75th percentile (OR, 1.7), obesity (BMI, 30-35; OR, 3.0), and lack of private health insurance (OR, 1.7) were marginally associated with increased odds of SSI.

CONCLUSIONS

Incisional SSI after abdominal hysterectomy was associated with increased BMI and blood transfusion. Longer duration of operation and lack of private health insurance were marginally associated with SSI.

Rates of surgical site infection as a performance measure: Are we ready?

With the introduction of quality assurance in health care delivery, there has been a proliferation of research studies that compare patient outcomes for similar conditions among many health care delivery facilities. Since the 1990s, increasing interest has been placed in the incorporation of clinical adverse events as quality indicators in hospital quality assurance programs. Adverse post-operative events, and very especially surgical site infection (SSI) rates after specific procedures, gained popularity as hospital quality indicators in the 1980s. For a SSI rate to be considered a valid indicator of the quality of care, it is essential that a proper adjustment for patient case mix be performed, so that meaningful comparisons of SSI rates can be made among surgeons, institutions, or over time. So far, a significant impediment to developing meaningful hospital-acquired infection rates that can be used for intra- and inter-hospital comparisons has been the lack of an adequate means of adjusting for case mix. This paper discusses what we have learned in the last years regarding risk adjustment of SSI rates for provider performance assessment, and identifies areas in which significant improvement is still needed.

Accounting for incomplete postdischarge follow-up during surveillance of surgical site infection by use of the National Nosocomial Infections Surveillance system's risk index

OBJECTIVE

We examined the usefulness of a simple method to account for incomplete postdischarge follow-up during surveillance of surgical site infection (SSI) by use of the National Nosocomial Infections Surveillance (NNIS) system's risk index.

DESIGN

Retrospective cohort study that used data prospectively collected from 1993 through 2006.

SETTING

Five private, nonuniversity healthcare facilities in Belo Horizonte, Brazil.

PATIENTS

Consecutive patients undergoing the following NNIS operative procedures: 20,981 operations on the genitourinary system, 11,930 abdominal hysterectomies, 7,696 herniorraphies, 6,002 cholecystectomies, and 6,892 laparotomies.

METHODS

For each operative procedure category, 2 SSI risk models were specified. First, a model based on the NNIS system's risk index variables was specified (hereafter referred to as the NNIS-based model). Second, a modified model (hereafter referred to as the modified NNIS-based model), which was also based on the NNIS system's risk index, was specified with a postdischarge surveillance indicator, which was assigned the value of 1 if the patient could be reached during follow-up and a value of 0 if the patient could not be reached. A formal comparison of the capabilities of the 2 models to assess the risk of SSI was conducted using measures of calibration (by use of the Pearson goodness-of-fit test) and discrimination (by use of receiver operating characteristic curves). Goodman-Kruskal correlations (G) were also calculated.

RESULTS

The rate of incomplete postdischarge follow-up varied between 29.8% for abdominal hysterectomies and 50.5% for cholecystectomies. The modified NNIS-based model for laparotomy did not show any significant benefit over the NNIS-based model in any measure. For all other operative procedures, the modified NNIS-based model showed a significantly improved discriminatory ability and higher G statistics, compared with the NNIS-based model, with no significant impairment in calibration, except if used to assess the risk of SSI after operations on the genitourinary system or after a cholecystectomy.

CONCLUSIONS

Compared with the NNIS-based model, the modified NNIS-based model added potentially useful clinical information regarding most of the operative procedures. Further work is warranted to evaluate this method for accounting for incomplete postdischarge follow-up during surveillance of SSI.

Risk factors for surgical site infection after major breast operation

BACKGROUND

Understanding surgical site infection (SSI) risk factors after breast operation is essential to develop infection-prevention strategies and improve surgical outcomes.

METHODS

We performed a retrospective case-control study with subjects selected from a cohort of mastectomy, breast reconstruction, and reduction surgical patients between January 1998 and June 2002 at a university-affiliated hospital. SSI cases within 1 year after operation were identified using ICD-9-CM diagnosis codes for wound infection and complication or positive wound cultures, or both. Medical records of 57 patients with breast SSI and 268 randomly selected uninfected control patients were reviewed. Multivariate logistic regression was used to identify independent risk factors for SSI.

RESULTS

Significant independent risk factors for breast incisional SSI included insertion of a breast implant or tissue expander (odds ratio [OR] = 5.3; 95% CI, 2.5 to 11.1), suboptimal prophylactic antibiotic dosing (OR = 5.1; 95% CI, 2.5 to 10.2), transfusion (OR = 3.4; 95% CI, 1.3 to 9.0), mastectomy (OR = 3.3; 95% CI, 1.4 to 7.7), previous chest irradiation (OR = 2.8; 95% CI, 1.2 to 6.5), and current or recent smoking (OR = 2.1; 95% CI, 0.9 to 4.9). Local infiltration of an anesthetic agent was associated with substantially reduced odds of SSI (OR = 0.4; 95% CI, 0.1 to 0.9).

CONCLUSIONS

Suboptimal prophylactic antibiotic dosing is a potentially modifiable risk factor for SSI after breast operation. SSI risk was increased in patients undergoing mastectomy and in patients who had an implant or tissue expander placed during operation. This information can be used to develop a specific risk stratification index to predict SSI and infection-preventive strategies tailored for breast surgery patients.

Surgical site infections in Italian Hospitals: a prospective multicenter study

BACKGROUND

Surgical site infections (SSI) remain a major clinical problem in terms of morbidity, mortality, and hospital costs. Nearly 60% of SSI diagnosis occur in the postdischarge period. However, literature provides little information on risk factors associated to in-hospital and postdischarge SSI occurrence. A national prospective multicenter study was conducted with the aim of assessing the incidence of both in-hospital and postdisharge SSI, and the associated risk factors.

METHODS

In 2002, a one-month, prospective national multicenter surveillance study was conducted in General and Gynecological units of 48 Italian hospitals. Case ascertainment of SSI was carried out using standardized surveillance methodology. To assess potential risk factors for SSI we used a conditional logistic regression model. We also reported the odds ratios of in-hospital and postdischarge SSI.

RESULTS

SSI occurred in 241 (5.2%) of 4,665 patients, of which 148 (61.4%) during in-hospital, and 93 (38.6%) during postdischarge period. Of 93 postdischarge SSI, sixty-two (66.7%) and 31 (33.3%) were detected through telephone interview and questionnaire survey, respectively. Higher SSI incidence rates were observed in colon surgery (18.9%), gastric surgery (13.6%), and appendectomy (8.6%). If considering risk factors for SSI, at multivariate analysis we found that emergency interventions, NNIS risk score, pre-operative hospital stay, and use of drains were significantly associated with SSI occurrence. Moreover, risk factors for total SSI were also associated to in-hospital SSI. Additionally, only NNIS, pre-operative hospital stay, use of drains, and antibiotic prophylaxis were associated with postdischarge SSI.

CONCLUSION

Our study provided information on risk factors for SSI in a large population in general surgery setting in Italy. Standardized postdischarge surveillance detected 38.6% of all SSI. We also compared risk factors for in-hospital and postdischarge SSI, thus providing additional information to that of the current available literature. Finally, a large amount of postdischarge SSI were detected through telephone interview. The evaluation of the cost-effectiveness of the telephone interview as a postdischarge surveillance method could be an issue for further research.

An alternative scoring system to predict risk for surgical site infection complicating coronary artery bypass graft surgery

OBJECTIVE

To analyze the risk factors for surgical site infection (SSI) complicating coronary artery bypass graft (CABG) surgery and to create an alternative SSI risk score based on the results of multivariate analysis.

METHODS

A prospective cohort study involving inpatient and laboratory-based surveillance of patients who underwent CABG surgery over a 27-month period from January 1, 2003 through March 31, 2005. Data were obtained from 6 acute care hospitals in Victoria, Australia, that contributed surveillance data for SSI complicating CABG surgery to the Victorian Hospital Acquired Infection Surveillance System Coordinating Centre and the Australasian Society of Cardiac and Thoracic Surgeons, also in Victoria.

RESULTS

A total of 4,633 (93%) of the 4,987 patients who underwent CABG surgery during this period were matched in the 2 systems databases. There were 286 SSIs and 62 deep or organ space sternal SSIs (deep or organ space sternal SSI rate, 1.33%). Univariate analysis revealed that diabetes mellitus, body mass index (BMI) greater than 35, and receipt of blood transfusion were risk factors for all types of SSI complicating CABG surgery. Six multivariate analysis models were created to examine either preoperative factors alone or preoperative factors combined with operative factors. All models revealed diabetes and BMI of 30 or greater as risk factors for SSI complicating CABG surgery. A new preoperative scoring system was devised to predict sternal SSI, which assigned 1 point for diabetes, 1 point for BMI of 30 or greater but less than 35, and 2 points for BMI of 35 or greater. Each point in the scoring system represented approximately a doubling of risk of SSI. The new scoring system performed better than the National Nosocomial Infections Surveillance System (NNIS) risk index at predicting SSI.

CONCLUSION

A new weighted scoring system based on preoperative risk factors was created to predict sternal SSI risk following CABG surgery. The new scoring system outperformed the NNIS risk index. Future studies are needed to validate this scoring system.