cqvip:Objective: To evaluate concurrent and predictive validity for low-contrast le tter acuity (L-CLA) testing as a candidate visual component for the Multiple Sc lerosis Functional Composite (MSFC). Methods: L-CLA testing was conducted in tw o MS patient cohorts. In the MSFC Validation Study, 137 participants from a Phas e III trial of inteferon beta-1a (Avonex) for relapsing-remitting MS werefoll owed. A second cohort included 65 patients with secondary progressive MS who par ticipated in a substudy of the International MS Secondary Progressive Avonex Con trolled Trial (IMPACT). The total number of letters read correctly at four contr ast levels (100, 5, 1.25, and 0.6%)was correlated with Expanded Disability Stat us Scale (EDSS), MSFC, Sickness Impact Profile, Multiple Sclerosis Quality of Li fe Inventory, and brain parenchymal fraction (BPF), as determined by MRI. Result s: Low-and high-contrast letter acuity scores correlated with BPF at follow-u p in the MSFC Validation Study (5%: r=0.40, p < 0.0001; 100%: r=0.31, p=0.0002 ). L-CLA also correlated with EDSS (5%: r=-0.35, p < 0.0001; 1.25%: r=-0.26 , p=0.0003) and MSFC(5%: r=0.47, p < 0.0001; 1.25%: r=0.45, p < 0.0001). In th e IMPACT Substudy, change in L-CLA scores from baseline to year 1 predicted sub sequent change in the EDSS from year 1 to 2 at the 5%(p=0.0142) and the 1.25%( p=0.0038) contrast levels, after adjusting for change in MSFC scores from baseli ne to year 1. Conclusions: Low-contrast letter acuity (L-CLA) scores demonstra te concurrent and predictive validity in patients with relapsing-remitting and secondary progressive multiple sclerosis (MS). L-CLA testing provides additiona l information relevant to the MS disease process that is not entirely captured b y the Multiple Sclerosis Functional Composite.
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