Validation of an instrument for measuring chronic pain in nursing homes

Background. Assessment of chronic pain is frequently done in care centers. The aim of this study was to analyze the psychometric properties of the Chronic Pain Grade Scale (CPGS) - that measures both the intensity of chronic pain and its incapacitating effects on the everyday activities of the elderly. Method. Cross-sectional study of 185 people with chronic pain from two nursing homes. The questionnaire was adapted by back-translation and administered as a structured interview. It was assessed for reliability, internal consistency, construct validity, convergent and divergent validity (regarding the SF-12 score) and discriminant validity. Studied variables were compared among the pain groups derived from applying the scale. Results. The scale showed sufficient reliability (alpha= 0.90), bidimensionality (intensity and disability), good convergent and divergent validity and sufficient discriminant validity. Elderly people in groups I and II had better physical health than those in groups III and IV, but group II people had similar mental health to those from group IV (highest/limiting disability). Males, people with no education and pensioners were more frequently classified as group IV. Conclusion. The Spanish version of the CPGS has proved to be valid and reliable for evaluating both intensity and disability related to chronic pain in older people living in nursing homes.