Variations in functioning and disability in multiple sclerosis. A two-year prospective study.

The aim of the present study was to explore variations in functioning and disability--with regard to cognition, manual dexterity, walking, energy, mood, activities of daily living and social/ lifestyle activities--every six months during a 2-year period, in 200 people with MS (PwMS) at an outpatient MS specialist clinic. Symbol Digit Modalities Test, Nine Hole Peg Test, Timed 25 Foot Walk, Fatigue Severity Scale, Beck Depression Inventory, Katz ADL Index Extended and Frenchay Activities Index were used to collect data. For analyses of statistically significant changes in scores during the study period, repeated measures ANOVA was used for ratio data and Friedman ANOVA for ordinal data. In addition, effect size as well as the mean/median change in score during the study period were determined for each functioning. Nearly all functioning studied varied significantly but there was no general deterioration in the sample. Small effect sizes were mainly found for the Frenchay Activities Index and a plausible practice effect was detected for the Symbol Digit Modalities Test. As many as 63% with regard to walking and 46% with regard to manual dexterity demonstrated >20% mean change in scores which has proved to be a reliable and clinically meaningful change. This study illustrates the importance of systematic and regular multidimensional assessment of functioning and disability in PwMS aiming to identify disabilities that could be minimized through timely and appropriate evidence-based interventions. The fluctuation in functioning and the conceivable learning effect inherent in instruments used should be taken into consideration when designing studies and interpreting the results.