This technical supplement summarises methods used to calculate descriptive statistics of performance indicators presented in Hospital Performance: Healthcare-associated Staphylococcus aureus bloodstream infections in 2011–12. Due to the complexity of the methods used, this supplement is targeted at individuals with technical expertise in the creation and use of health information.
Hospital Performance: Healthcare-associated Staphylococcus aureus bloodstream infections in 2011–12 publishes statistics on the case counts and rates of the healthcare-associated Staphylococcus aureus (S. aureus) bloodstream infections (referred to clinically as bacteraemia) for hospitals covered by a healthcare-associated infection surveillance program.
The aim was to allow fairer comparisions between infection rates in public hospitals after accounting for the fact that each facility:
- Serves patients that vary in the degree to which they are vulnerable to infections and/or
- Provides treatments and procedures that vary in the degree to which they put patients at risk of acquiring an infection.
The challenge was to achieve this aim using two information systems - one that provides hospital-level information about the number of cases of healthcare-associated S. aureus bloodstream infection and patient bed days under surveillance, and the other that provides patient-level information on inpatient services.
The Authority undertook to risk-adjust hospital-level rates of S. aureus bloodstream infections but, following analysis and consultation, concluded that reliable estimates could not be created for reasons described in this supplement.
Therefore, the Authority created a peer classification system specific for reporting healthcare-associated S. aureus bloodstream infections that improves the comparability of hospital rates of infection.
The Authority identified eight hospital peer risk groups using a two-tiered classification method based on hospital size and hospital type (tier 1), and hospital-level prevalence of immunosuppression among patients and treatments or procedures that create opportunities for patient infection (tier 2).
The application of these two tiers resulted in the following eight peer groups:
- Major hospitals, more vulnerable patients
- Major hospitals, fewer vulnerable patients
- Large hospitals, more vulnerable patients
- Large hospitals, fewer vulnerable patients
- Medium hospitals, more vulnerable patients
- Medium hospitals, fewer vulnerable patients
- Small hospitals, more vulnerable patients
- Small hospitals, fewer vulnerable patients.
Cases and rates are available online for specialist women’s and children’s and ‘other’ hospitals. Comparisons are not made among these hospitals.
Please note: This technical supplement relates only to the report Hospital Performance: Healthcare-associated Staphylococcus aureus bloodstream infections in 2011–12, published May 2013.
The most up-to-date results for each hospital are available on the hospital results pages and the most-up-to-date methods are summarised in the About the data pages.