Validity of the Central Sensitization Inventory (CSI) through Rasch analysis in patients with knee osteoarthritis

Introduction/objective: Central sensitization (CS) is a known contributor to chronic pain in people with knee osteoarthritis (KOA) and is commonly measured by psychophysical testing or patient-reported methods such as the Central Sensitization Inventory (CSI). However, previous studies have shown a weak association between the two. We therefore sought to evaluate the validity of the CSI through Rasch analysis in patients with KOA. Method: We performed a secondary analysis of a multicenter cohort study with patients with KOA consulting orthopedic surgeons. Rasch analysis was conducted considering person factors of age, sex, BMI, pain intensity, pain catastrophizing, and quantitative sensory test findings using pressure pain thresholds and temporal summation to assess how the CSI fits to the Rasch model (supporting validity). We used RUMM2030 software to model fit estimates, making adjustments as required to achieve model fit (P > 0.05). Results: Data from 293 patients were included (58.7% female, mean age 63.6 years, 49.1% obese) Initial evaluation with Rasch modelling indicated misfit. Eleven of 25 items on the CSI displayed disordered thresholds which were rescored by collapsing response categories until the thresholds demonstrated sequential progression. Reanalysis demonstrated persistent model misfit so a subtest was developed to address local dependency of 6 items. Thereafter, model fit was achieved (P = 0.071, indicating not differing from Rasch model) and acceptable unidimensionality (P = 0.068 with 95% CI 0.043–0.093). Conclusions: The CSI was able to be fit to the Rasch model after rescoring while retaining all 25 items. The unidimensionality validates CS as measured by the CSI as a singular construct.Key Points• The Central Sensitization Inventory (CSI) was able to be fit to the Rasch model after rescoring while retaining all 25 items.• The unidimensionality of the CSI validates CS as a singular construct.• Our results suggest rescoring of the CSI for people with KOA, but it should be confirmed and replicated in larger samples prior to clinical use.