Translation, adaptation and validation of the Bulgarian version of the King’s Parkinson’s Disease Pain Scale

BACKGROUND: The purpose of the present study was to translate and cross-culturally adapt the King’s Parkinson’s Disease Pain Scale (KPPS) into Bulgarian and to investigate its psychometric properties in order to provide a validated Parkinson’s disease-specific pain instrument in Bulgarian language (KPPS-BG). METHODS: Translation into Bulgarian and a cultural adaptation were performed to obtain KPPS-BG. A total of 162 patients with idiopathic Parkinson’s disease were screened for pain using the complementary to the KPPS questionnaire – King’s Parkinson’s Disease Pain Questionnaire (KPPQ). KPPS-BG domain and total scores were calculated and internal consistency, construct validity and test-retest reliability were examined for 129 patients having one or more positive items in the KPPQ-BG. RESULTS: 79.6 % of the patients reported one or more types of pain. The most common type was musculoskeletal pain (83.7 %), followed by nocturnal pain (55.0 %), fluctuation-related pain (50.1 %), radicular pain (43.4 %), chronic pain (31.0 %), discoloration, edema/swelling (27.1 %) and, oro-facial pain (14.3 %). Mean KPPS-BG total score was 21.1 ± 17.3 SD. KPPS-BG showed a good reliability (Cronbach’s alpha 0.75). The test-retest reliability of the KPPS-BG was high and the intraclass correlation coefficient was 0.92, demonstrating а good repeatability. KPPS-BG total score was higher in patients with postural instability gait difficulty motor subtype, compared to tremor-dominant or indeterminate subtype. Significant positive correlations were found between KPPS-BG total score and modified H&Y, Movement Disorders Society Unified Parkinson’s Disease Rating Scale part III. CONCLUSIONS: The KPPS-BG constitutes a reliable, comprehensive and useful tool for pain assessment in native Bulgarian patients with Parkinson’s disease.