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Do You Know Your Hospital’s True Surgical Site Infection Rate?

Reported surgical site infection (SSI) rates—whether from your own hospital, clinical literature, or national reporting—may be missing a significant portion of the actual SSIs that are occurring in patients following surgery.

One key obstacle in understanding a hospital's true SSI rate is that methods used for reporting SSIs vary across institutions, national databases, literature, and public reporting. Truly understanding what SSI data is telling you – or not telling you – requires careful evaluation of the data source.  Several recent studies provide us with valuable insight on this issue.

A Tower of Babel: Different Reporting Mechanisms, Definitions, and Data Sources

There are many different mechanisms used for reporting SSI rates both nationally and locally within hospitals.  Each of these reported numbers may utilize different definitions and/or different sources of information. 

Operating Hospital vs. Other Hospitals

A recent study by Yokoe et al. was published in Clinical Infectious Diseases looking at the impact of hospital rankings based on limiting the reporting of SSI outcomes to only the hospital where the initial operation took place. Utilizing data from a California statewide hospital registry including over 60,059 colon surgeries and 64,918 abdominal hysterectomies, the study found that 7.2% of SSIs in colon surgery and 13.4% of SSIs in abdominal hysterectomy would have been missed by utilizing SSI surveillance of the operative hospital alone. The authors concluded that "standard SSI surveillance that mainly focuses on infections detected at the operative hospital causes varying degrees of SSI under-estimation, leading to inaccurate assignment or avoidance of financial penalties for approximately one in eleven to sixteen hospitals."

Inpatient vs. Outpatient

Beyond excluding SSI rates occurring at other hospitals, administrative databases also tend to exclude SSIs reported as an outpatient. SSIs are diagnosed in the outpatient setting in nearly half the cases (41%-49%); therefore, administrative databases used to identify infections for public reporting are likely to significantly underreport the rate of SSI.2,3 In a study comparing the National Healthcare Safety Network (NHSN) to the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP), which generally includes a dedicated nurse to abstract the data on a small sampling of patients, the NSHN SSI rate was 5.7% compared to 13.5% in ACS NSQIP, demonstrating an approximately 42% difference.4 This study found that in most cases an outpatient SSI would not have been captured by the current NHSN reporting practices.4 A separate study of surgical site infection surveillance data in colon procedures similarly identified 34% underreporting by hospitals submitting data to NHSN.5

Superficial vs. Deep vs. Organ Space

It is also important to understand what SSIs are being included within the reported rates (superficial, deep, and/or organ space).  For example, the colorectal SSI rate, used by CMS to determine payment penalties and displayed on the public reporting website (Hospital Compare), looks only at deep and organ space SSIs related to colorectal surgery. From review of the literature about two-thirds of colorectal SSIs are superficial2,6-8, therefore the number being publicly reported on the Hospital Compare website is significantly lower than the overall SSI rate being experienced by the patient.

The Method Matters

It is also evident that SSI rates vary greatly depending on the method used to collect the data. 

Twelve studies were reviewed for SSI rate in colorectal surgery.2,3,6,7,9-16 The mean SSI rate reported across all studies was 15.3%.  The rate of SSI varied greatly depending on the method used to collect the data, ranging from 3.7% in an administrative database to 27.6% in a prospective study.2,16

Eyes on the Prize

Granted, reporting and surveillance of SSI and HAIs is a gray area. More will need to be done to help hospitals determine the best way to improve the process. Leading infection prevention experts are calling for better guidelines around surveillance and reporting.

While the challenges around SSI reporting continue to be addressed, the best front-line infection prevention teams keep their eyes on the prize:  zero-preventable infections and doing all they can to achieve that important goal.   


1 Yokoe DS, Avery TR, Platt R, Kleinman K, Huang SS. Ranking Hospitals Based on Colon Surgery and Abdominal Hysterectomy Surgical Site Infection Outcomes: Impact of Limiting Surveillance to the Operative Hospital. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 2018.

2 Tanner J, Khan D, Aplin C, Ball J, Thomas M, Bankart J. Post-discharge surveillance to identify colorectal surgical site infection rates and related costs. J Hosp Infect. 2009;72(3):243-250.

3 Smith RL, Bohl JK, McElearney ST, et al. Wound infection after elective colorectal resection. Ann Surg. 2004;239(5):599-605; discussion 605-597.

4 Ju MH, Ko CY, Hall BL, Bosk CL, Bilimoria KY, Wick EC. A comparison of 2 surgical site infection monitoring systems. JAMA Surg. 2015;150(1):51-57.

5 Backman LA, Carusillo E, D'Aquila L N, Melchreit R, Fekieta R. Validation of surgical site infection surveillance data in colon procedures reported to the Connecticut Department of Public Health. Am J Infect Control. 2017;45(6):690-691.

6 Watanabe A, Kohnoe S, Shimabukuro R, et al. Risk factors associated with surgical site infection in upper and lower gastrointestinal surgery. Surg Today. 2008;38(5):404-412.

7 Keenan JE, Speicher PJ, Thacker JK, Walter M, Kuchibhatla M, Mantyh CR. The preventive surgical site infection bundle in colorectal surgery: an effective approach to surgical site infection reduction and health care cost savings. JAMA Surg. 2014;149(10):1045-1052.

8 Esemuede IO, Murray AC, Lee-Kong SA, Feingold DL, Kiran RP. Obesity, regardless of comorbidity, influences outcomes after colorectal surgery-time to rethink the pay-for-performance metrics? J Gastrointest Surg. 2014;18(12):2163-2168.

9 Wick EC, Vogel JD, Church JM, Remzi F, Fazio VW. Surgical site infections in a "high outlier" institution: are colorectal surgeons to blame? Dis Colon Rectum. 2009;52(3):374-379.

10 Sutton E, Miyagaki H, Bellini G, et al. Risk factors for superficial surgical site infection after elective rectal cancer resection: a multivariate analysis of 8880 patients from the American College of Surgeons National Surgical Quality Improvement Program database. J Surg Res. 2017;207:205-214.

11 Adegboyega TO, Borgert AJ, Lambert PJ, Jarman BT. Applying the National Surgical Quality Improvement Program risk calculator to patients undergoing colorectal surgery: theory vs reality. Am J Surg. 2017;213(1):30-35.

12 Wick EC, Shore AD, Hirose K, et al. Readmission rates and cost following colorectal surgery. Dis Colon Rectum. 2011;54(12):1475-1479.

13 Wick EC, Hirose K, Shore AD, et al. Surgical site infections and cost in obese patients undergoing colorectal surgery. Arch Surg. 2011;146(9):1068-1072.

14 Walz JM, Paterson CA, Seligowski JM, Heard SO. Surgical site infection following bowel surgery: a retrospective analysis of 1446 patients. Arch Surg. 2006;141(10):1014-1018; discussion 1018.

15 de Lissovoy G, Fraeman K, Hutchins V, Murphy D, Song D, Vaughn BB. Surgical site infection: incidence and impact on hospital utilization and treatment costs. Am J Infect Control. 2009;37(5):387-397.

16 Mahmoud NN, Turpin RS, Yang G, Saunders WB. Impact of surgical site infections on length of stay and costs in selected colorectal procedures. Surg Infect (Larchmt). 2009;10(6):539-544.