Clustering a large Spanish sample of patients with fibromyalgia using the Fibromyalgia Impact Questionnaire–Revised: differences in clinical outcomes, economic costs, inflammatory markers, and gray matter volumes

Abstract

The main objective of this study is to identify fibromyalgia syndrome (FMS) clusters using the Revised Fibromyalgia Impact Questionnaire (FIQR), and to examine whether the clusters differ in sociodemographic characteristics, clinical measures, direct and indirect costs, levels of inflammatory markers, and brain morphometry. A hierarchical cluster analysis was performed to classify a large, pooled Spanish sample of patients with FMS (N = 947) using the FIQR as clustering variable. A latent profile analysis was subsequently conducted to confirm the optimal number of FMS clusters. To examine external validity, a battery of clinical measures, economic costs, inflammatory markers, and gray matter volumes of relevant cortical and subcortical areas were analyzed. We also compared the discriminant validity of the clusters with the original FIQR severity categories. To promote the implementation in real-world clinical practice, we built a free online cluster calculator. Our findings indicated that a four-cluster solution more clearly captured the heterogeneity of FIQR data and provided the best fit. This cluster solution allowed for detection of differences for most clinical outcomes and economic costs. Regarding the inflammatory and brain-based biomarkers, differences were found in C-reactive protein, and tendencies were found in the right medial prefrontal cortex, the right parahippocampal gyrus, and the right middle cingulate cortex; brain regions associated with executive functions and pain processing. The original FIQR categories presented similar results, although their precision in discriminating among the nonextreme categories (ie, moderate and severe) was not sound. These findings are discussed in relation to previous research on FMS clustering.

Machine Learning to Understand the Immune-Inflammatory Pathways in Fibromyalgia

“…The WPI, SSS, and FS scores were significantly higher in FM than in controls. The severity of FM as assessed with FIQ-R in FM patients was moderate [27], and they suffered from FM for 13.0 (±9.5) years. All clinical rating scale scores were significantly different between the two groups.…”

Associations of Cognitive Fusion and Pain Catastrophizing with Fibromyalgia Impact through Fatigue, Pain Severity, and Depression: An Exploratory Study Using Structural Equation Modeling

“…It is widely accepted that a moderate-to-strong association exists between functional limitation and pain severity [1][2][3]. However, pain severity is not the only factor associated with the impact of the syndrome and functional limitations are known to vary across patients reporting similar pain severity levels [4,5]. Thus, it has been argued that functional limitation in patients with FM and other pain conditions should be conceptualized within a more comprehensive biopsychosocial perspective [6].…”

Patients With Fibromyalgia Reporting Severe Pain but Low Impact of the Syndrome: Clinical and Pain‐Related Cognitive Features

“…Widespread pain is the cardinal symptom in FM and has a major effect on quality of life . However, pain is not the only factor explaining the impact of the syndrome, as the latter is known to vary across patients reporting similar pain severity levels . This study focuses on investigating the psychological correlates of patients with FM characterized by high adaptability to severe levels of pain, that is, patients in an extreme scenario of success showing low overall impact of the syndrome despite experiencing severe pain.…”