Confirmatory factor analysis and Rasch analysis of the German revised version of the Niigata PPPD questionnaire: NPQ-R

Introduction: Persistent Postural-Perceptual Dizziness (PPPD) is a chronic func tional vestibular disorder exacerbated by posture, movement, or visual stimuli. Widely used dizziness questionnaires lack specificity for PPPD symptoms. The Niigata PPPD Questionnaire (NPQ) and its German-translated and revised ver sion (NPQ-R), including two additional subscales, were developed to address this gap. Its internal consistency, convergent validity, and test–retest reliability were found to be satisfactory. The aim of the present study was to examine the NPQ R’s structure using confirmatory factor analysis (CFA) and Rasch item analysis. Materials and methods: We analysed data from 265 (135 female) patients (50.2 ± 16.8 years, dizziness duration 46.3 ± 76.6 months) who completed the NPQ-R. CFA was conducted using the robust maximum likelihood estimator in R (lavaan), and Rasch item analysis was performed for each subscale separately. Results: CFA revealed moderate-to-high covariances between the five latent variables (range: 0.59–0.97), with all items except one demonstrating significant standardised loadings. Rasch analysis indicated acceptable item fit for most items. Person separation reliability ranged from 0.63 to 0.75 across subscales. Item 2 (Visual Stimulation) exhibited misfit. Discussion: The NPQ-R demonstrates promising psychometric properties. While the Rasch analyses support reliability and internal coherence, the CFA results sug gest that the overall five-factor model may require refinement. Conceptual clar ity and wording of specific items should be re-examined. However, the NPQ-R remains suitable for PPPD assessment and severity determination in clinical and research contexts, while theoretical and empirical refinement of its factor struc ture is recommended