Psychometric features of Neuropathic Pain Symptom Inventory in Iranian people with Parkinson's disease.

OBJECTIVE: Neuropathic pain is a type of pain reported in people with Parkinson's disease. There are various scales to evaluate the characteristics of this kind of pain. The purpose of this study was to investigate the psychometric properties of the Neuropathic Pain Symptom Inventory (NPSI), a specific scale that measures neuropathic pain in Iranian people with Parkinson's disease. METHOD: Four hundred forty-seven individuals with Parkinson's disease were recruited in the study. Acceptability, internal consistency (Cronbach's alpha), and test-retest reliability (intraclass correlation coefficient, ICC) of NPSI were calculated. Dimensionality was examined through exploratory factor analysis. For convergent validity, correlations of NPSI with Douleur Neuropathic 4, Brief Pain Inventory, King's Pain Parkinson disease Scale, and Visual Analog Scale-Pain were used. Discriminative validity and sensitivity to change between On- and Off- medication states were analyzed. RESULTS: A marked floor effect was observed for this scale (64.2%). Cronbach's alpha and ICC were 0.90 and 0.87, respectively. Items of NPSI were placed in 4 factors. A moderate to the strong association (rs = 0.55 to 0.85) between NPSI and other scales was obtained. The results of discriminative validity and sensitivity to change indicate the ability of NPSI to show differences between medication states. CONCLUSION: The results of this study suggest that NPSI has acceptable reliability, validity, and sensitivity to change, indicating that this scale is suitable for measuring neuropathic pain in Iranian people with Parkinson's disease.

King's Parkinson's disease pain scale cut-off points for detection of pain severity levels: A reliability and validity study.

BACKGROUND: Pain is one of the most common non-motor symptoms in Parkinson's disease (PD). Using an appropriate and specific measuring tool would be helpful in managing the pain. King's Parkinson's disease Pain Scale (KPPS) is an instrument designed to specifically measure pain in people with PD. PURPOSE: This study aimed to examine the psychometric properties of the Persian version of KPPS (KPPS-P) and its cut-off points for pain severity levels. METHODS: A total of 480 people with PD (with a mean (SD) age of 60.89 (10.98)) were recruited. The acceptability of KPPS-P was calculated. The structural validity and discriminant validity for different levels of pain was explored via the factor analysis, and Receiver Operating Characteristics (ROC) curves, respectively. Internal consistency, test-retest, and inter-rater reliability were estimated by Cronbach's alpha and Interclass Correlation coefficient (ICC). Convergent validity was established between KPPS-P and other scales including Visual Analog Scale-Pain, Douleur Neuropathic 4, Brief Pain Inventory, Short-form McGill Pain Questionnaire-2, and Parkinson's Disease-8. RESULTS: A significant floor effect was observed. The exploratory factor analysis revealed 4 factors. Cronbach's alpha and ICC values were higher than 0.80. The correlation range between KPPS-P and other scales was 0.35-0.76. Cut-off points of 0, 17, and 68 were obtained to discriminate pain severity levels between no pain, mild, moderate, and severe pain, respectively, with sensitivity and specificity above 0.80. CONCLUSION: Our results indicate that the Persian version of KPPS not only has acceptable psychometric properties to assess pain in PD but also has the ability to distinguish between different levels of pain severity.