Construction and validation of the chronic acquired polyneuropathy patient‐reported index, “CAP‐PRI:” a disease‐specific, health‐related quality of life instrument

Generic health-related quality-of-life (HRQOL) patient-reported outcome measures have been used in patients with chronic immune-mediated polyneuropathies. We have created a disease-specific HRQOL instrument.The chronic acquired polyneuropathy patient-reported index (CAP-PRI) was developed and validated in multiple steps. Items were initially generated through patient and specialist input. The performance of the preliminary 20 items was analyzed via a prospective, 5-center study involving chronic immune-mediated polyneuropathy patients.Data analysis suggested modification to a 15-item scale with 3 response categories rather than 5. The final CAP-PRI was validated in another prospective, 5-center study. The CAP-PRI appeared to be a unidimensional outcome measure that fit the Rasch model in our multicenter cohort. It correlated appropriately with outcome measures commonly used in this patient population.The CAP-PRI is a simple disease-specific HRQOL measure that appears to be useful for clinical care and possibly also for clinical trials. Muscle Nerve 54: 9-17, 2016.