Trends in Canadian hospital standardised mortality ratios and palliative care coding 2004-2010: a retrospective database analysis.

BACKGROUND: The hospital standardised mortality ratio (HSMR), anchored at an average score of 100, is a controversial macromeasure of hospital quality. The measure may be dependent on differences in patient coding, particularly since cases labelled as palliative are typically excluded.

OBJECTIVE: To determine whether palliative coding in Canada has changed since the 2007 national introduction of publicly released HSMRs, and how such changes may have affected results.

DESIGN: Retrospective database analysis.

SETTING: Inpatients in Canadian hospitals from April 2004 to March 2010.

PATIENTS: 12 593 329 hospital discharges recorded in the Canadian Institute for Health Information (CIHI) Discharge Abstract Database from April 2004 to March 2010.

MEASUREMENTS: Crude mortality and palliative care coding rates. HSMRs calculated with the same methodology as CIHI. A derived hospital standardised palliative ratio (HSPR) adjusted to a baseline average of 100 in 2004-2005. Recalculated HSMRs that included palliative cases under varying scenarios.

RESULTS: Crude mortality and palliative care coding rates have been increasing over time (p<0.001), in keeping with the nation's advancing overall morbidity. HSMRs in 2008-2010 were significantly lower than in 2004-2006 by 8.55 points (p<0.001). The corresponding HSPR rises dramatically between these two time periods by 48.83 points (p<0.001). Under various HSMR scenarios that included palliative cases, the HSMR would have at most decreased by 6.35 points, and may have even increased slightly.

LIMITATIONS: Inability to calculate a definitively comparable HSMR that include palliative cases and to account for closely timed changes in national palliative care coding guidelines.

CONCLUSIONS: Palliative coding rates in Canadian hospitals have increased dramatically since the public release of HSMR results. This change may have partially contributed to the observed national decline in HSMR.