ABSTRACT
This chapter presents a very limited summary of the steps that would be required to examine any clinical case definition for the fibromyalgia syndrome (FMS). The development and validation of a clinically useful case definition for FMS would necessarily be a multistage process. It would require large numbers of subjects with FMS and a similarly large number of subjects without FMS. Once content validity has been determined, the next step should be cluster analysis. This would help to avoid the problem of tautology that often has been a concern with the 1990 ACR criteria. Eligible subjects who agree to participate should then complete a health questionnaire asking about all of the symptoms and signs contained within the proposed case definition. Then each of the eligible subjects in the cluster analysis study should be examined by two to three examiners blinded both to pre-existing diagnoses and to the findings and conclusions of earlier examiners.
