P.023 The Pain in Dystonia Scale (PIDS): development and validation

Abstract

Background: Pain in a common symptom in adult-onset idiopathic dystonia (AOID). An appropriate tool to understand this symptom is needed to improve AOID patients’ care. We developed a rating instrument for pain in AOID and validated it in cervical dystonia (CD). Methods: Development and validation of the Pain in Dystonia Scale (PIDS) in three phases: 1. International experts and participants generated and evaluated the preliminary items for content validity; 2. The PIDS was drafted and revised, followed by cognitive interviews to ensure suitability for self-administration; and 3. the clinimetric properties of the final PIDS were assessed in 85 participants. Results: PIDS evaluates pain severity (by body part), functional impact and external modulating factors. It showed high test-retest reliability the total score (0.9, p<0.001), intraclass correlation coefficients higher than 0.7 for all items and high internal consistency (Cronbach’s alpha 0.9). Convergent validity analysis revealed a strong correlation between the PIDS severity score and the TWSTRS pain subscale (0.8, p<0.001), the brief pain inventory short form (0.7, p<0.001) and impact of pain on daily functioning (0.7, p<0.001). Conclusions: The PIDS is the first specific questionnaire developed to evaluate pain in patients with AOID with high-level clinimetric properties in people with CD.