Relationship between preventable hospital deaths and other measures of safety: an exploratory study.

OBJECTIVE: To explore associations between the proportion of hospital deaths that are preventable and other measures of safety. DESIGN: Retrospective case record review to provide estimates of preventable death proportions. Simple monotonic correlations using Spearman's rank correlation coefficient to establish the relationship with eight other measures of patient safety. SETTING: Ten English acute hospital trusts. PARTICIPANTS: One thousand patients who died during 2009. RESULTS: The proportion of preventable deaths varied between hospitals (3-8%) but was not statistically significant (P = 0.94). Only one of the eight measures of safety (Methicillin-resistant Staphylococcus aureus bacteraemia rate) was clinically and statistically significantly associated with preventable death proportion (r = 0.73; P < 0.02). There were no significant associations with the other measures including hospital standardized mortality ratios (r = -0.01). There was a suggestion that preventable deaths may be more strongly associated with some other measures of outcome than with process or with structure measures. CONCLUSIONS: The exploratory nature of this study inevitably limited its power to provide definitive results. The observed relationships between safety measures suggest that a larger more powerful study is needed to establish the inter-relationship of different measures of safety (structure, process and outcome), in particular the widely used standardized mortality ratios.