Validity of the Central Sensitization Inventory compared with traditional measures of disease severity in fibromyalgia

Objective The goal of this study was to explore additional evidence of convergent and discriminant validity of the Central Sensitization Inventory (CSI) in a large sample of subjects with fibromyalgia (FM). Methods Patients were consecutively enrolled for a cross-sectional assessment comprehensive of three FM-specific measures (the revised Fibromyalgia Impact Questionnaire [FIQR], the modified Fibromyalgia Assessment Status [modFAS], and the Polysymptomatic Distress Scale [PDS]) and of CSI. To test the convergent validity, the Spearman's rho was used to measure the degree of correlation between the variables CSI and the FM-specific measures. To assess discriminant validity, CSI scores were grouped according to FIQR disease severity states, and differences between these groups studied with the Kruskal-Wallis test. Interpretative cutoffs were established with the interquartile reconciliation approach. Results The study included 562 FM patients, 199 (35.4%) were classified as having central sensitization syndrome (CSI >= 40). CSI was largely correlated with modFAS (rho = 0.580; p < 0.0001), FIQR (rho = 0.542; p < 0.0001), and PDS (rho = 0.518; p < 0.0001). The differences between the CSI scores in accordance with the FIQR were significant (p < 0.000001). CSI cutoffs proposed for FM: 21 between remission and mild severity, 30 between mild and moderate severity, 37 between moderate and severe disease, and 51 between severe and very severe disease. Conclusion The current study successfully showed additional evidence of the convergent and discriminant validity of the CSI in FM patients.