Outcome measures in immune-mediated neuropathies: the need to standardize their use and to understand the clinimetric essentials.

Peripheral neurological disorders like neuropathies may cause impairments (such as weakness and sensory deficits), which may lead to problems in daily life and social functioning with a possible decrement in quality of life expectations. Choosing the proper outcome measure to evaluate the therapeutic efficacy of an intervention at one of these levels of outcome should therefore be considered as fundamental to the design of randomized trials in peripheral neurological disorders. However, these choices are dependent not only on the proposed research purposes but also, and perhaps more importantly, on the fulfillment of the scientific needs of these measures. With an increasing demand for accuracy, a thorough and comprehensive evaluation of an outcome measure is needed to determine its simplicity, communicability, validity, reliability, and responsiveness before being clinically applicable, techniques that are being captured by the science of clinimetrics. Most neurologists are still unfamiliar with these rigorous methodological essentials or overlook some of them in their trial preparations because these are considered time consuming and mind numbing. This review will highlight, against the background of the international classification framework and clinimetric needs for outcome measures, the selected scales applied in published randomized controlled trials in patients with Guillain-Barré syndrome, chronic inflammatory demyelinating polyradiculoneuropathy, multifocal motor neuropathy, and gammopathy-related neuropathies. The need for comparison responsiveness studies between equally valid and reliable measures and to standardize their use is emphasized in these conditions. Finally, specific recommendations are given to move from classic to modern clinimetric approach when constructing, evaluating, and selecting outcome measures using new methods like Rasch analysis, accentuating the need of shifting toward a more modern era.