AND RELEVANCE In a broad review of published literature , risk factors for SSI were characterized as describing reduced fitness , patient frailty , surgery duration , and complexity .
IMPORTANCE Surgical site infection ( SSI ) complicates 2 - 5 % of surgeries in the United States .
Severity of SSI ranges from superficial skin infection to life-threatening conditions such as severe sepsis , and SSIs are responsible for increased morbidity , mortality , and economic burden associated with surgery .
Staphylococcus aureus ( S. aureus ) is a commonly-isolated organism for SSI , and methicillin-resistant S. aureus SSI incidence is increasing globally .
OBJECTIVE The objective of this systematic review was to characterize risk factors for SSI within observational studies describing incidence of SSI in a real-world setting .
Identification of risk factors by systematic review and development of risk-adjusted models for surgical site infection.
BACKGROUND  Surgical site infections ( SSIs ) are complications of surgery that cause significant postoperative morbidity . SSI has been proposed as a potential indicator of the quality of care in the context of clinical governance and monitoring of the performance of NHS organisations against targets . OBJECTIVES We aim ed to address a number of objectives . Firstly , identify risk factors for SSI , criteria for stratifying surgical procedures and evidence about the importance of postdischarge surveillance ( PDS ) . Secondly , test the importance of risk factors for SSI in surveillance data bases and investigate interactions between risk factors . Thirdly , investigate and vali date different definitions of SSI . Lastly , develop models for making risk-adjusted comparisons between hospitals . DATA SOURCES A single hospital surveillance data base was used to address objectives 2 and 3 and the UK Surgical Site Infection Surveillance Service data base to address objective 4 . STUDY DESIGN There were four elements to the research : ( 1 ) systematic review s of risk factors for SSI ( two review ers assessed titles and abstract s of studies identified by the search strategy and the quality of studies was assessed using the Newcastle Ottawa Scale ) ; ( 2 ) assessment of agreement between four SSI definitions ; ( 3 ) validation of definitions of SSI , quantifying their ability to predict clinical outcomes ; and ( 4 ) development of operation-specific risk models for SSI , with hospitals fitted as r and om effects . RESULTS Review s of SSI risk factors other than established SSI risk indices identified other risk ; some were operation specific , but others applied to multiple operations . The factor most commonly identified was duration of preoperative hospital stay . The review of PDS for SSI confirmed the need for PDS if SSIs are to be compared meaningfully over time within an institution . There was wide variation in SSI rate ( SSI% ) using different definitions . Over twice as many wounds were classified as infected by one definition only as were classified as infected by both . Different SSI definitions also classified different wounds as being infected . The two most established SSI definitions had broadly similar ability to predict the chosen clinical outcomes . This finding is paradoxical given the poor agreement between definitions . Elements of each definition not common to both may be important in predicting clinical outcomes or outcomes may depend on only a subset of elements which are common to both . Risk factors fitted in multivariable models and their effects , including age and gender , varied by surgical procedure . Operative duration was an important risk factor for all operations , except for hip replacement . Wound class was included least often because some wound classes were not applicable to all operations or were combined because of small numbers . The American Association of Anesthesiologists class was a consistent risk factor for most operations . CONCLUSIONS The research literature does not allow surgery-specific or generic risk factors to be defined . SSI definitions varied between surveillance programmes and potentially between hospitals . Different definitions do not have good agreement , but the definitions have similar ability to predict outcomes influenced by SSI . Associations between components of the National Nosocomial Infections Surveillance risk index and odds of SSI varied for different surgical procedures . There was no evidence for effect modification by hospital . Estimates of SSI% should be disseminated within institutions to inform infection control . Estimates of SSI% across institutions or countries should be interpreted cautiously and should not be assumed to reflect quality of medical care . Future research should focus on developing an SSI definition that has satisfactory psychometric properties , that can be applied in everyday clinical setting s , includes PDS and is formulated to detect SSIs that are important to patients or health services . FUNDING The National Institute for Health Research Technology Assessment programme
AND RELEVANCE In a broad review of published literature , risk factors for SSI were characterized as describing reduced fitness , patient frailty , surgery duration , and complexity .
IMPORTANCE Surgical site infection ( SSI ) complicates 2 - 5 % of surgeries in the United States .
Severity of SSI ranges from superficial skin infection to life-threatening conditions such as severe sepsis , and SSIs are responsible for increased morbidity , mortality , and economic burden associated with surgery .
Staphylococcus aureus ( S. aureus ) is a commonly-isolated organism for SSI , and methicillin-resistant S. aureus SSI incidence is increasing globally .
OBJECTIVE The objective of this systematic review was to characterize risk factors for SSI within observational studies describing incidence of SSI in a real-world setting .