Objective: To better understand the remaining three-fold disparity between adverse event (AE) rates in the Quality in Australia Health Care Study (QAHCS) and the Utah-Colorado Study (UTCOS) after methodological differences had been accounted for.
Setting: Iatrogenic injury in hospitalized patients in Australia and America.
Design: Using a previously developed classification, all AEs were assigned to 98 exclusive descriptive categories and the relative rates compared between studies; they were also compared with respect to severity and death.
Main outcome measures: The distribution of AEs amongst the descriptive and outcome categories.
Results: For 38 categories, representing 67% of UTCOS and 28% of QAHCS AEs, there were no statistically significant differences. For 33, representing 31% and 69% respectively, there was seven times more AEs in QAHCS than in UTCOS. Rates for major disability and death were very similar (1.7% and 0.3% of admissions for both studies) but the minor disability rate was six times greater in QAHCS (8.4% versus 1.3%).
Conclusions: A similar 2% core of serious AEs was found in both studies, but for the remaining categories six to seven times more AEs were reported in QAHCS than in UTCOS. We hypothesize that this disparity is due to different thresholds for admission and discharge and to a greater degree of under-reporting of certain types of problems as AEs by UTCOS than QAHCS reviewers. The biases identified were consistent with, and appropriate for, the quite different aims of each study. No definitive difference in quality of care was identified by these analyses or a literature review.