Preventable drug-related hospital admissions.

Objective: To estimate the prevalence of preventable drug-related hospital admissions (PDRAs) and to explore if selected study characteristics affect prevalence estimates.

Methods: Keyword search of MEDLINE (1966-December 1999), International Pharmaceutical Abstracts (1970-December 1999), and hand search. Two reviewers independently selected studies published in peer-reviewed journals and extracted crude prevalence estimates and study characteristics. Trials had to specifically address consequences of drug therapy requiring hospital admission and include a quantitative preventability assessment. Stratified analysis and meta-regression were used to explore the association between study characteristics and prevalence estimates.

Data Synthesis: Fifteen studies reported a median PDRA prevalence of 4.3% (interquartile range [IQR] 3.1-9.5%). The median preventability rate of drug-related admissions was 59% (IQR 50-73%). No evidence of publication bias related to study size could be determined. Because the individual study results were highly heterogeneous (Cochran's Q = 176, df = 14; p < 0.001), no meta-analytic summary estimate was computed. Stratified analysis suggested an association between prevalence estimates and 3 study characteristics: exclusion of first admissions (readmission studies: average PDRA prevalence of 14.0 %, estimated prevalence OR = 3.7); mean age of admissions >70 (OR = 2.1); and inclusion of "indirect" drug-related morbidity, such as omission errors or therapeutic failure (OR = 1.9). There was little evidence of other associations with prevalence estimates, such as selection of specific hospital units, exclusion/inclusion of planned admissions, country, and specified methods of PDRA case ascertainment.

Conclusions: Drug-related morbidity is a significant healthcare problem, and a great proportion is preventable. Study methods in prevalence reports vary and should be considered when interpreting findings or planning future research.