Measuring function and health status in rheumatic disease clinical trials.

We have summarized the limitations of traditional outcome measures in rheumatology, reviewed the growing field of measures emphasizing the patient's perception of improvement, and provided guidelines for choosing a specific instrument for a clinical trial. Newer measures have measurement properties equal to or surpassing traditional measures, but no one ADL or quality-of-life instrument can be used to assess outcome in every situation as no one test can indicate success of a treatment in a chronic disease. An instrument needs to be judged by the following criteria: Is it metrically sound? Does it fit the socio-demographic characteristics of the target population? Does it measure the specific changes which are likely to be affected by the treatment? Will it capture or measure the expected changes?