Thirty-day readmission, mortality rates may blur true hospital performance

By Sarah Guy, medwireNews Reporter

Thirty-day readmission and mortality rates are highly variable according to the extent data are adjusted for potential confounding factors, and whether readmissions are considered per hospital or per patient, indicate Canadian study results.

The findings imply the need for caution when evaluating hospital performance based on these measures, suggest Carl van Walraven (University of Ottowa, Ontario, Canada) and colleagues in the Canadian Medical Association Journal.

"To measure quality of care, one would ideally measure the number of avoidable readmissions," says the team, believing that models that are able to adjust for such potentially confounding variables as patient comorbidities are preferable for this type of analysis.

"Regardless, the model's accuracy should be clearly stated to inform readers of its effectiveness for leveling the playing field among hospitals," write van Walraven et al.

Using data for all Ontario-based hospital patients discharged alive between January 2005 and December 2010, the authors determined rates of death or readmission within 30 days. A total of 3,148,648 admissions to 162 hospitals for 1,802,704 patients occurred during this period.

The overall proportion of discharges followed by a death or urgent readmission within 30 days ranged from 4.6% to 20.0% per hospital.

Furthermore, mean observed-to-expected ratios for death or readmission varied for each measure evaluated, report the researchers, from 0.94 for all admissions and single admissions per patient, adjusted for all measurable factors (length of stay, acuity of admission, patient comorbidity, emergency department use 6 months prior to admission), to 1.11 and 1.14 for all admissions and single admissions, respectively, adjusted for patient age and gender.

Adjustment for patient age and gender alone gave the greatest variation among hospitals, note van Walraven and co-workers.

Hospital-specific comparisons also varied considerably, with an average annual range of 31% for observed-to-expected ratios of readmission or death (as a percentage of the overall readmission rate for that hospital) using any of the four ratios: all admissions adjusted for age and gender or all measurable factors, and one-per-patient admissions adjusted for age and gender or all measurable factors.

"Until we know how best to measure rates of avoidable readmission using administrative data, we need to rely on face validity to determine which method is preferable for measuring hospital-specific postdischarge outcomes," conclude the researchers.

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