Studies using English administrative data (Hospital Episode Statistics) to assess health-care outcomes--systematic review and recommendations for reporting.

BACKGROUND Studies using English administrative data from the Hospital Episode Statistics (HES) are increasingly used for the assessment of health-care quality. This study aims to catalogue the published body of studies using HES data to assess health-care outcomes, to assess their methodological qualities and to determine if reporting recommendations can be formulated. METHODS Systematic searches of the EMBASE, Medline and Cochrane databases were performed using defined search terms. Included studies were those that described the use of HES data extracts to assess health-care outcomes. RESULTS A total of 148 studies were included. The majority of published studies were on surgical specialties (60.8%), and the most common analytic theme was of inequalities and variations in treatment or outcome (27%). The volume of published studies has increased with time (r = 0.82, P < 0.0001), as has the length of study period (r = 0.76, P < 0.001) and the number of outcomes assessed per study (r = 0.72, P = 0.0023). Age (80%) and gender (57.4%) were the most commonly used factors in risk adjustment, and regression modelling was used most commonly (65.2%) to adjust for confounders. Generic methodologic data were better reported than those specific to HES data extraction. For the majority of parameters, there were no improvements with time. CONCLUSIONS Studies published using HES data to report health-care outcomes have increased in volume, scope and complexity with time. However, persisting deficiencies related to both generic and context-specific reporting have been identified. Recommendations have been made to improve these aspects as it is likely that the role of these studies in assessing health care, benchmarking practice and planning service delivery will continue to increase.