In-hospital mortality for ICU patients is often used as a quality measure, but discharge practices may bias results in a way that disadvantages large academic hospitals, according to a recently conducted study by researchers in the University of Pittsburgh School of Medicine and University of Michigan. The authors stated that hospitals differ in the number of patients they transfer to other hospitals or post-acute care facilities and these differences can affect in-hospital mortality measurement if some hospitals discharge patients more frequently or earlier than others, since in these cases the mortality burden is shifted to other facilities. While it’s known that discharge practices alter in-hospital ICU mortality measurement, it was previously unknown whether this effect is uniform across hospitals or whether certain types of hospitals are more affected than others.
The authors found that this ‘discharge bias’ disproportionally hurts large hospitals and academic hospitals, which frequently accept many patients in transfer from other hospitals. Hospitals that care for a large number of patients insured through health maintenance organizations (HMOs) are also affected, since these organizations typical restrict transfers. Mortality measures tied to a specific time point, such as 30-day mortality, are less biased by discharge practices but are harder to calculate.
The retrospective cohort study used data on 43,830 ICU patients admitted to 134 hospitals in Pennsylvania in 2008. Discharge bias was defined as 30-day mortality minus in-hospital mortality; greater discharge bias makes a hospital appear of relatively higher quality.
The study concludes that large academic hospitals, as well as hospitals with a high proportion of commercial HMO patients, are more negatively affected by using in-hospital ICU mortality compared to 30-day mortality than other hospitals. Accounting for this bias might prevent these hospitals from being unfairly penalized in public reporting or pay-for-performance programs.