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 functional 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 version (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 suggest that the overall five-factor model may require refinement. Conceptual clarity 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 structure is recommended.