A comparison of iatrogenic injury studies in Australia and the USA I: context, methods, casemix, population, patient and hospital characteristics

Objective. To better understand the differences between two iatrogenic inju ry studies of hospitalized patients in 1992 which used ostensibly similar m ethods and similar sample sizes, but had quite different findings. The Qual ity in Australian Health Care Study (QAHCS) reported that 16.6% of admissio ns were associated with adverse events (AE), whereas the Utah, Colorado Stu dy (UTCOS) reported a rate of 2.9%. Setting. Hospitalized patients in Australia and the USA. Design. Investigators from both studies compared methods and characteristic s and identified differences. QAHCS data were then analysed using UTCOS met hods. Main outcome measures. Differences between the studies and the comparative AE rates when these had been accounted for. Results. Both studies used a two-stage chart review process (screening nurs e review followed by confirmatory physician review) to detect AEs; five imp ortant methodological differences were found: (i) QAHCS nurse reviewers ref erred records that documented any link to a previous admission, whereas UTC OS imposed age-related dme constraints; (ii) QAHCS used a lower confidence threshold for defining medical causation; (iii) QAHCS used mio physician re viewers, whereas UTCOS used one; (iv) QAHCS counted all AEs associated with an index admission whereas UTCOS counted only those determining the annual incidence; and (v) QAHCS included some types of events not included in UTC OS. When the QAHCS data were analysed using UTCOS methods, the comparative rates became 10.6% and 3.2%, respectively Conclusions. Five methodological differences accounted for some of the disc repancy between the two studies. Two explanations for the remaining three-f old disparity are that quality of care was worse in Australia and that medi cal record content and/or reviewer behaviour was different.