Skip to main content Accessibility help
×
Home

SIR, You've Led Me Astray!

  • David Birnbaum (a1), Roxie Zarate (a1) and Anthony Marfin (a1)

Abstract

Background.

The standardized infection ratio (SIR) is an indirectly standardized morbidity ratio that has been used to compare the infection rate in a hospital with an expected number of infections from a national standard and is being increasingly promoted as a metric for the public reporting of healthcare-associated infections (HAIs).

Objective.

To identify potential discrepancies between SIR and other measures of risk.

Methods.

Hypothetical and real data were compared using relative risk, a directly standardized morbidity ratio, and SIR values across a range of varying hospital population compositions.

Results.

In real and hypothetical data, other summary statistics were consistent with each other and with underlying HAI incidence density rates. However, use of the SIR frequently led to conclusions inconsistent with these other inherently unbiased estimators.

Conclusion.

Because of a recognized type of distortion inherent in the calculation of indirectly standardized ratios, use of the SIR can lead to conclusions that differ from those reached when using other traditional measures of risk and to incorrect assessments of conclusions about the performance of hospitals or states. In addition, the tendency to inappropriately arrange SIR values in rank order for comparison makes SIR unsuitable as a statewide metric for monitoring HAIs.

Copyright

Corresponding author

Washington State Department of Health, HAI Program, PO Box 47811, Olympia, WA (david.birnbaum@doh.wa.gov)

References

Hide All
1.Culver, D, Horan, T, Gaynes, R. Comparing surgical site infection (SSI) rates using the NNIS SSI risk index and the standardized infection ratio. Am J Infect Control 1994;22(2):102.
2.Rothman, KJ. Modern epidemiology. Boston: Little, Brown, 1986.
3.US Department of Health and Human Services. HHS action plan to prevent healthcare-associated infections, http://www.hhs.gov/ash/initiatives/hai/index.html. Accessed February 8, 2011.
5.Centers for Disease Control and Prevention. First state-specific healthcare-associated infections summary data report CDC's National Healthcare Safety Network (NHSN) January-June, 2009. http://www.cdc.gov/hai/statesummary.html. Accessed May 27, 2010.
6.Reinberg, S. Decline in potentially lethal hospital-based infections. Bloomberg Businessweek. May 27, 2010. http://www.businessweek.com/lifestyle/content/healthday/639582.html?campaigned = rss_topEmailedStories. Accessed June 15, 2010.
7.Yule, GU. On some points relating to vital statistics, more especially statistics of occupational methods. J R Stat Soc 1934;97:184.
8.Cochrane, WG. Sampling techniques. 3rd ed. New York: Wiley, 1977.
9.Gustafson, TL. Practical risk-adjusted quality control charts for infection control. Am J Infect Control 2000;28(6):406414.
10.Delgado-Rodríguez, M, Llorca, J. Caution should be exercised when using the standardized infection ratio. Infect Control Hosp Epidemiol 2005;26(1):89.
11.Gustafson, TL. Three uses of the standardized infection ratio (SIR) in infection control. Infect Control Hosp Epidemiol 2006;27(4):427430.
12.Narong, MN, Thongpiyapoom, S, Thaikul, N, et al.Surgical site infections in patients undergoing major operations in a university hospital: using standardized infection ratio as a benchmarking tool. Am J Infect Control 2003;31:274279.
13.Jodra, VM, Rodela, AR, Martínez, FM, Fresneña, NL. 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. Infect Control Hosp Epidemiol 2003;24(10):744748.
14.Kasatpibal, N, Jamulitrat, S, Chongsuvivatwong, V, et al.Standardized incidence rates of surgical site infection: a multicenter study in Thailand. Am J Infect Control 2005;33(10):587594.
15.Jodrá, VM, Díaz-Agero Pérez, C, Sainz de los Torreros Soler, L, et al.Results of the Spanish national nosocomial infection surveillance network (VICONOS) for surgery patients from January 1997 through December 2003. Am J Infect Control 2006;34(3): 134141.
16.Rioux, C, Grandbastien, B, Astagneau, P. The standardized incidence ratio as a reliable tool for surgical site infection surveillance. Infect Control Hosp Epidemiol 2006;27(8):817824.
17. Centers for Medicare and Medicaid Services, 42 CFR §412, §413, §415, §424, §440, §441, §482, §485, and §489. http://www.gpo.gov/fdsys/pkg/FR-2010-08-16/html/2010-19092.htm. Accessed February 8, 2011.

Related content

Powered by UNSILO

SIR, You've Led Me Astray!

  • David Birnbaum (a1), Roxie Zarate (a1) and Anthony Marfin (a1)

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed.