Hospital quality indicators are utilized for the comparison of hospital performance and individual hospital monitoring as well as benchmarking health care services of provinces and countries [1–5]. A quality indicator based on patient outcomes has three essential elements: the medical diagnosis, the time to measured outcome (e.g. death, readmission, surgery), and the place of the outcome (e.g. hospital, home, institution). Mortality has been widely evaluated as a quality indicator [6–13].
Large variation in hospital ranking and outlier detection has been found when mortality measures were calculated by different methods [9, 14–16]. An inherent problem with in-hospital mortality is that it reflects to a great degree hospital discharge practices [9, 16]. Hospitals discharging patients early may seem to perform better than hospitals with longer patient stay. For patients treated at more than one hospital (transferred patients), the outcome should be attributed to all involved hospitals . However, double-counting of patients may introduce bias [13, 15].
A mortality-based indicator should include all-cause, in-and-out-of hospital deaths within a standardized follow-up period, e.g. 30 days. Data on in-hospital deaths is readily available, but obtaining data including out-of-hospital deaths and transfer information may be a challenge. Studies have found that for some medical conditions, the hospital profiles were similar when comparing mortality calculated from in-hospital deaths and in-and-out-of hospital deaths within 30 days (counting from start of admission, regardless of cause) [9, 17]. Others report differences depending on time, place and cause of death included for the mortality measurement [10, 15, 16, 18–20]. However, for transferred patients, previous studies have attributed the outcome to the first or the last hospital in the chain of admissions or used single-hospital stays only [16, 18, 19]. To our knowledge, no previous study has attributed the outcome to all involved hospitals without double counting.
First time acute myocardial infarction (AMI), stroke and hip fracture are three common, serious and resource-demanding medical conditions. They were selected by the Norwegian Directorate for Health and Social Affairs for developing mortality as a quality indicator for Norwegian hospitals . All permanent residents in Norway have a personal identification number (PIN) which enables linking between hospital data and official registers. This offers a unique opportunity to compare mortality measures that differ with respect to time and place of death and to study the impact of transfers at the national level.
The objectives of the present work were to: i) summarize time, place and cause of death for patients hospitalized with AMI, stroke and hip fracture, ii) compare risk-adjusted mortality measures based on both in-hospital deaths and in-and-out-of- hospital deaths, with and without patients transferred to other hospitals.