Abstract
Policy Points The use of standardized mortality rates (SMRs) to profile hospitals presumes differences in preventable deaths, and at least one health system has suggested measuring preventable death rates of hospitals for comparison across time or in league tables. The influence of reliability on the optimal review number per case note or hospital for such a program has not been explored. Estimates for preventable death rates using implicit case note reviews by clinicians are quite low, suggesting that SMRs will not work well to rank hospitals, and any misspecification of the risk-adjustment models will produce a high risk of mislabelling outliers. Most studies achieve only fair to moderate reliability of the direct assessment of whether a death is preventable, and thus it is likely that substantial numbers of reviews of deaths would be required to distinguish preventable from nonpreventable deaths as part of learning from individual cases, or for profiling hospitals. Furthermore, population- and hospital system-specific data on the variation in preventable deaths or adverse events across the hospitals and providers to be compared are required in order to design a measurement procedure and the number of reviews needed to distinguish between the patients or hospitals. CONTEXT: There is interest in monitoring avoidable or preventable deaths measured directly or indirectly through standardized mortality rates (SMRs). While there have been numerous studies in recent years on adverse events, including preventable deaths, using implicit case note reviews by clinicians, no systematic reviews have aimed to summarize the estimates or the variations in methodologies used to derive these estimates. We reviewed studies that use implicit case note reviews to estimate the range of preventable death rates observed, the measurement characteristics of those estimates, and the measurement procedures used to generate them. We comment on the implications for monitoring SMRs and illustrate a way to calculate the number of reviews needed to establish a reliable estimate of the preventability of one death or the hospital preventable death rate. METHODS: We conducted a systematic review of the literature supplemented by a reanalysis of authors' previously published and unpublished data and measurement design calculations. We conducted initial searches in PubMed, MEDLINE (OvidSP), and ISI Web of Knowledge in June 2010 and updated them in June 2012 and December 2017. Eligibility criteria included studies of hospital-wide admissions from general and acute medical wards where preventable death rates are provided or can be estimated and that can provide interobserver variations. FINDINGS: Twenty-three studies were included from 1985 to 2017. Recent larger studies suggest consistently low rates of preventable deaths (interquartile range of 3.0%-6.0% since 2008). Reliability of a single review for distinguishing between individual cases with regard to the preventability of death had a Kappa statistic of 0.10-0.50 for deaths and 0.21-0.76 for adverse events. A Kappa of 0.35 would require an average of 8 to 17 reviews of a single case to be precise enough to have confidence in high-stakes decisions to change care procedures or impose sanctions within a hospital as a result. No study estimated the variation in preventable deaths across hospitals, although we were able to reanalyze one study to obtain an estimate. Based on this estimate, 200 to 300 total case note reviews per hospital could be required to reliably distinguish between hospitals. The studies displayed considerable heterogeneity: 13/23 studies defined preventable death with a threshold of greater than or equal to four in a six-category Likert scale and 11/24 involved a two-stage screening process with nurses at the first stage and physicians at the second. Fifteen studies provided expert clinical review support for reviewer disagreements, advice, and quality control. A "generalist/internist" was the modal physician specialty for reviewers and they received one to three days of generic tools orientation and case note review practice. Methods did not consider the influence of human or environmental factors. CONCLUSIONS: The literature provides limited information about the measurement characteristics of preventable deaths, suggesting that substantial numbers of reviews may be needed to create reliable estimates of preventable deaths at the individual or hospital level. Any operational program would require population-specific estimates of reliability. Preventable death rates are low, which is likely to make it difficult to use SMRs based on all deaths to validly profile hospitals. The literature provides little information to guide improvements in the measurement procedures.