Despite showing acceptable psychometric properties, the criterion validity of the original Fibromyalgia Rapid Screening Tool (FiRST) has been called into question for including insufficiently challenging comparison groups. Consequently our objective was to validate a Spanish version of the FiRST including pain disorders more analogous to fibromyalgia.
The FiRST was translated following international standards. Internal consistency and temporal stability were assessed. The ability of the FiRST global score as a screening tool for fibromyalgia (criterion validity) was assessed by logistic regression analysis. To determine the degree to which potential confounders might affect the criterion validity of the FiRST (divergent validity), it was reassessed by hierarchical multivariate logistic regression, entering demographics in a first step, followed by pain, anxiety and depression, catastrophizing, disability and the FiRST global score in a last step.
The final sample comprised 257 patients (67% cases of fibromyalgia). The Spanish version of the FiRST showed acceptable internal consistency, reliability and criterion validity. The FiRST was able to discriminate between fibromyalgia and non-fibromyalgia patients even after controlling for the effect of potential confounders. However, both criterion and divergent validity were challenged by a moderate specificity.
The Spanish version of the FiRST may be used as a screening tool for fibromyalgia even in those patients whose cognitive style is characterized by catastrophizing about pain and high levels of functional disability, anxiety and depression. The clinical consequences of the moderate specificity shown by this Spanish version of the FiRST are discussed.