[Classification of fibromyalgia. A systematic review of the literature].

OBJECTIVE To review the scientific literature concerning the classification of fibromyalgia (FM), including previous studies focusing on the gnosologic evaluation of FM, with the aim of proposing a classificatory hypothesis based on the current scientific evidence. METHODS Systematic review using a baseline MEDLINE search. Search terms included «fibromyalgia» and «classification». Additional articles were identified through a comprehensive manual search of the references of retrieved articles. RESULTS This systematic review has identified, on the one hand, several classificatory proposals based on psychopathological aspects, and, on the other hand, the key role of associated diseases. Based on the scientific evidence currently available, the following FM subsets were defined: patients with no associated processes (type I FM), patients with associated rheumatic/autoimmune chronic diseases (type II FM), patients with severe psychiatric disorders (type III FM) and patients with simulated FM (type IV FM). CONCLUSIONS Few studies have specifically analysed the classification of FM into subgroups with a more homogeneous clinical expression. Correct classification of patients with FM requires the integration of two key concepts (psychopathological evaluation and coexistence of comorbid processes), with an individual diagnostic evaluation by a multidisciplinary team.