Comparative evaluations of neuroperformance and clinical outcome assessments in chronic progressive multiple sclerosis: I. reliability,validity and sensitivity to disease progression

Abstract

There remains controversy regarding the most sensitive and valid outcome assessments to use in multiple sclerosis (MS) clinical trials. A double blind, placebo controlled, parallel group multicenter clinical trial to evaluate the clinical efficacy of cyclosporine A in chronic progressive MS incorporated several major clinical and performance outcome assessment modalities and a large sample size, both of which provide a unique opportunity to explore the relationship among MS disease status and the various outcome measures over time. The measures included a structured neurological examination, the Kurtzke Functional System scales and Expanded Disability Status Score, and the Incapacity Status Scale from the MS Minimal Record of Disability, die Harvard Ambulation Index, and neuroperformance testing. A test-retest reliability index, principal component analyses and a signal-to-noise ratio metric were used to comparatively evaluate the reliability, validity and sensitivity to disease progression of the various outcome assessments. The goal was to provide a rational basis for selection of behavioral outcome assessments in future MS clinical trials by identifying the primary dimensions of MS measured by the candidate outcome assessments and providing an objective basis for selecting tests that are most sensitive to MS disease and its progression over a two year trial period. We conclude that the components of the major clinical and performance measures show excellent reliability and cross validation. Principal component analyses of all outcome assessments yielded six primary underlying factors for describing disease status in chronic progressive MS that included lower extremity/pyramidal dysfunction, cerebellar/brainstem and upper extremity dysfunction, somatosensory dysfunction, visual dysfunction, mental or intellectual dysfunction and bowel/bladder problems. Signal-to-noise ratios indicated that upper and lower extremity composites of neuroperformance test kerns provided the most sensitive indicators of MS disease progression in the placebo group over the 2 year trial period.