Subgrouping patients with fibromyalgia according to the results of the fibromyalgia impact questionnaire: a replication study

Fibromyalgia is a complex and heterogeneous disease, and several attempts have been made in order to identify different subgroups of patients sharing a common symptomatology. The purpose of the present study has been to replicate a subgroup classification proposed by de Souza et al. based in the Fibromyalgia Impact Questionnaire (FIQ) in a large sample of patients with a cultural and clinical setting different from the original one. Four hundred twenty-one patients were classified, according to the results of the visual analog FIQ subscales in type I o type II subgroups. Demographic and clinical data, as well as results of scales assessing disease's severity, quality of life, sleep quality, anxiety and depression, were compared between the two groups. The profiles of type I and type II patients from our sample strikingly paralleled those of the original study, demonstrating the reproducibility of the classification. In our sample, 18.8% of the patients appertained to type I subgroup and 81.2% to type II subgroup. Patients from this later subgroup had higher comorbidity and received more drugs than those of the former. They were also more physically ill, with higher FIQ total scores and worse sleep quality, and more psychologically distressed, with higher levels of anxiety and depression and lower scores in the mental component summary of the Short-Form Health Questionnaire (SF-12). Our study shows that the proposed fibromyalgia classification is reliable and easy to perform and could be applied in further studies.