Validity of fibromyalgia survey questionnaire (2016) assessed by telephone interview and cross-cultural adaptation to Brazilian Portuguese language.

To verify the validity of the 2016-revised Fibromyalgia Survey Questionnaire (FSQ) by telephone interview compared to self-administration and to produce a valid version of FSQ in Brazilian Portuguese language.
The Brazilian version of FSQ was produced following the recommendations for cross-cultural adaptation. Validity of Brazilian FSQ self-administration was assessed by checking agreement of its results with fibromyalgia diagnosis according the 1990 American College of Rheumatology (ACR) criteria. Reproducibility and validity of FSQ by telephone were assessed by comparing its results with the previous FSQ self-administration.
A Brazilian Portuguese version (FSQ-Brazil) was produced. FSQ-Brazil had good internal consistency (Cronbach’s alpha between 0.73 and 0.94). Agreement between the results obtained by self-administration of FSQ-Brazil and by telephone interview was substantial or almost perfect for almost all questions about pain sites and all questions about other somatic symptoms (Cohen’s kappa higher than 0.6). There were small but significant bias toward higher scores of widespread pain index and fibromyalgia severity scale in the telephone interview compared to self-administration. Fibromyalgia definition by self-administration and telephone interview with FSQ-Brazil both revealed substantial agreement with the diagnosis based on ACR 1990 criteria (Cohen’s kappa 0.62 and 0.65; respectively).
FSQ-Brazil demonstrated good internal consistency, reproducibility and validity both by self-administration and by telephone interview. However, caution must be taken with the interpretation of quantitative scores of widespread pain index and symptoms severity scale, which slightly differed according the method (self-administration or interview) in our study.