Measurement properties of the Brazilian online version of the Fibromyalgia Rapid Screening Tool (FiRST)

OBJECTIVE: The Fibromyalgia Rapid Screening Tool (FiRST) was developed to screen people with chronic pain for Fibromyalgia (FM), especially in primary health care settings. This study aimed to translate the FiRST into Brazilian Portuguese and evaluate its measurement properties for an online application. METHODS: After the process of translation and backtranslation, the FiRST was applied online in 483 adults with chronic pain (FM group n = 395; Chronic pain group n = 88), along with the Numerical Rating Scale for pain and fatigue, the Brief Pain Inventory, and the Fibromyalgia Impact Questionnaire-Revised. A Receiver Operating Characteristics (ROC) curve was computed and the area under the curve (AUC) was used to determine the sensibility, specificity, and cut-off score for the FiRST. The Mann-Whitney test was used for quantitative variables and the Chi-square and the Fisher’s exact test, for the categorical variables with level of significance of 5%. Fleiss’ Kappa, Gwet’s AC1 and percentage of agreement were also calculated between test and retest. RESULTS: For all the questionnaires, the FM group presented higher scores, which mean a worst condition. The FiRST presented a sensitivity of 92.3%, and a specificity of 61.6% with 5 as the cut-off score. AUC, Fleiss’ Kappa, Gwet’s AC1 and percentage of agreement were, respectively, 0.82, 0.38, 0.63 and 71.8%. CONCLUSION: The FiRST was translated into Brazilian Portuguese and the online version presented a good content validity and adequate measurement errors that allow FM patients to be screened among people with chronic pain.