Testing an instrument to screen for fibromyalgia syndrome in general population studies: the London Fibromyalgia Epidemiology Study Screening Questionnaire.

OBJECTIVE: To develop and test an instrument to screen for fibromyalgia syndrome (FM) in general population surveys.
METHODS: We designed a questionnaire with 4 pain and 2 fatigue items. A positive screen was defined 2 ways: (1) positive responses to all 4 items on pain, and (2) positive responses to all pain and fatigue items. Sensitivity was tested in the clinic on 31 outpatients with FM, specificity on 30 outpatients with rheumatoid arthritis (RA) and 30 healthy controls. Test-retest reliability (TRR) was estimated in a community survey of 672 noninstitutionalized adults. Positive predictive value (PPV) was estimated as part of a community survey of 3395 noninstitutionalized adults, in which 100 cases of FM were confirmed by examination.
RESULTS: For pain criteria alone sensitivity was 100% (95% confidence intervals 90.3%, 100%); in patients with RA specificity was 53.3% (35.4%, 71.2%). For the pain plus fatigue criteria, sensitivity was 93.5% (83.8%, 100%), and specificity in patients with RA 80% (65.7%, 94.3%). In nonpatient controls, specificity was 100% (89.3%, 100%) using either definition of a positive screen. For those initially screening negative, TRR was 100% (93.2%, 100%) using either definition. For positive screens, TRR was 95.0% (88.8%, 100%) for the pain criteria alone, and 81.0% (69.1%, 92.8%) for the combined criteria. PPV was 56.8% (53.0%, 60.6%) using the pain criteria alone, and 70.6% (CI 55.3%, 85.9%) using the combined criteria.
CONCLUSION: The instrument appears to be useful in screening for FM in general population surveys of noninstitutionalized adults. Confirmation of FM among those who screen positive requires a personal interview to reestablish pain duration and distribution, and an examination for tender points.