Identification of subgroups among fibromyalgia patients

Abstract

This paper presents some hypotheses concerning the identification of homogeneous subgroups among fibromyalgia (FM) patients in order to improve the management of the disease. It also reviews the available literature. Three methods for subgrouping are discussed according to clinical features, biomarkers and gait analysis. Clinical subgrouping based on cluster analysis has been used for the identification of homogeneous subgroups of patients and, more recently, homogeneous clinical features. Longitudinal studies using clinical subgroups to direct treatment and predict outcome are still required. Biomarkers in FM, which is a neurobiological disease, are proving to be of interest. Nonetheless, for the moment, none of them can be used to subgroup FM patients. Due to the fact that cortical and subcortical mechanisms of gait control share some cognitive functions which are involved in FM, gait markers have been proposed to evaluate and to subgroup FM patients in clinical settings. Three out of 4 core FM symptoms are linked to gait markers. Kinesia measured by means of cranio-caudal power is correlated to pain and could be proposed to assess pain behavior (kinesiophobia). Stride frequency (SF), which is linked to physical component, allows the identification of a hyperkinetic subgroup. Furthermore, SF has been correlated to fatigue during the 6-minute walking test. Stride regularity, which expresses the unsteadiness of gait, is correlated to cognitive dysfunction in FM. A reduction in stride regularity allows a homogeneous subgroup to be recognized that is characterized by increased anxiety and depression, and decreased cognitive functions. These results need to be validated in further studies before use in daily clinical practice.