The validity of indicators for assessing quality of care: a review of the European literature on hospital readmission rate.

BACKGROUND: Quality indicators are increasingly being implemented in Europe for policy and management purposes. Many of these indicators were initially developed and implemented in the USA. However, the suitability of directly adopting indicators that have been developed in a different health care system can be questioned. Therefore, we investigate the validity behind the readmission rate indicator in the European setting.
METHODS: A systematic literature study was conducted to identify the status of scientific research on the validity of this indicator (January 1999 and April 2010). Descriptive information as well as information on the data source, indicator definition, risk adjustment factors, and conclusions was assessed.
RESULTS: The majority of the 486 included studies focused on the actual use of the indicator as an outcome measure in European countries. Only 21 studies specifically addressed its validity, or important prerequisites of validity. There is little consensus over the time-frame used to calculate the indicator, the type of readmission that is included, and the case-mix adjustment applied.
CONCLUSIONS: Despite the increase in Europe of the use of the readmission rate as a measure of quality of care, the amount of research performed on its validity is scarce. Those studies that report on validity replicate earlier, mainly US findings (<1999) of methodological problems and express reservations on its large-scale use. The readmission rate as an indicator should be used with care. Users should address issues related to definition, time-frame and case-mix adjustment as part of the process to enhance validity in the European settings.