Validation and cross-cultural adaptation of the 'Fibromyalgia Participation Questionnaire' to the Spanish population: study protocol.

There are few high-quality instruments to evaluate the participation and social functioning of fibromyalgia patients. The Fibromyalgia Participation Questionnaire (FPQ) is a questionnaire that evaluates these aspects with high reliability and validity in its German original version. The aim of this work was to describe the translation and cross-cultural adaptation process of the FPQ into Spanish and its validation to ensure the equivalence against the original version. The questionnaire will be translated according to the FACIT methodology, and it will be tested in the Clinical Management Unit of North Almeria Health Area. This methodology includes several stages: double forward translation, reconciled version, back-translation, review of the previous versions and development of the prefinal version for the pretest. Once the pretest ends, the final version of the questionnaire will be developed, which will be subjected to a validation process to study its psychometric properties. Reliability will be studied by internal consistency and test-retest reliability through Cronbach's alpha and Pearson's correlation coefficient, respectively. External and construct validity will be analysed using correlation coefficients, content validity with an empirical analysis, and a differential item functioning analysis will be employed to measure discriminative validity. The presence of ceiling and floor effects will be calculated too. The validation of the FPQ into different languages will allow better evaluation and treatment based on the observed limitations fibromyalgia patients suffer from, as well as bringing the possibility to compare between other countries and generalize its use in the scientific community.