Psychometric longitudinal evaluation of the Chronic Acquired Polyneuropathy Patient-Reported Index (CAPPRI) in patients with Chronic Inflammatory Demyelinating Polyneuropathy.

BACKGROUND We studied the performance of a 15-item, health-related quality-of-life polyneuropathy scale in a longitudinal study of patients with chronic inflammatory demyelinating polyneuropathy (CIDP). METHODS Sixty-one patients with CIDP completed the Chronic Acquired Polyneuropathy Patient-Reported Index (CAPPRI) scale and Patient Impression of Change (PIC) at baseline and follow-up visits. Clinicians completed Inflammatory Neuropathy Cause and Treatment (INCAT) disability scores at baseline and follow-up visits. Conventional and modern psychometric analyses were performed on the completed forms. RESULTS CAPPRI was psychometrically stable between visits without significant difference in response pattern between visits 1 and 2 (paired t-test P = .72). There was strong correlation between changes in INCAT and changes in CAPPRI scores between two visits (rho = 0.6, P < .001). In addition, we showed robust CAPPRI effect sizes between PIC categories. CONCLUSIONS We demonstrated psychometric stability and construct longitudinal validity of CAPPRI.