Is it possible to measure prescribing quality using only prescription data?

A large number of prescribing quality indicators based on register data have been proposed and many are used routinely in quality management. Often the content and face validity of indicators have been assessed by consensus methods, but studies analysing other validity aspects are scarce. Prescription data are frequently used for indicators, but they do not provide any direct information about disease and patient factors important for judging the quality of prescribing. If register-based proxies for diagnoses, disease severity or risk factors are employed, validation is essential. The concurrent validity of indicators should be assessed by comparing to a "gold standard" quality assessment at the patient level using all available clinical information. The validity of frequently used quality indicators of asthma treatment has been questioned and should be further investigated. NSAID prescribing indicators are currently under evaluation. In the future, detailed clinical information from practice databases and computerised hospital records will be an important data source for indicators and for validation studies. Furthermore, the statistical and epidemiological properties of prescribing quality indicators need more attention.