The present study shows that Fibromyalgia Rapid Screening Tool (FiRST) was proved beneficial in assessing fibromyalgia credibly. The samples collected from different countries showed variation in results differing from high to low specificity which can aid in the diagnosis of this condition.

To assess the transcultural equivalency of the Spanish version of the Fibromyalgia Rapid Screening Tool (FiRST) and its discriminatory ability in different Latin American samples.

Departments of Rheumatology in general hospitals and private centers. Fibromyalgia unit in a university hospital.350 chronic pain patients from Spain, Argentina, Mexico, Peru, and Ecuador. The cultural relevance of the Spanish version of the FiRST was evaluated. The ability of the FiRST as a screening tool for fibromyalgia was assessed by logistic regression analysis. To determine the degree to which potential confounders, such as differences in demographics, pain, affective distress, catastrophizing, and disability, might affect the discriminatory ability, the tool was reassessed by hierarchical multivariate logistic regression.

Slightly different versions of the FiRST were recommended for use in each Latin American subsample. The FiRST showed acceptable criterion validity and was able to discriminate between fibromyalgia and non-fibromyalgia patients even after controlling for the effect of potential confounders. However, low specificities were observed in samples from Spain and Mexico.

The Spanish version of the FiRST may be used as a screening tool for fibromyalgia in several Latin American subsamples, even in those patients with high scores on potential confounders. In Spain and Mexico, the low specificity of the FiRST suggests, however, that it would be best used to support a suspected diagnosis of fibromyalgia, rather than to exclude the diagnosis.