A cross-sectional study of hand function in inclusion body myositis – implications for functional rating scale

ABSTRACT Inclusion body myositis (IBM) is a slowly progressive and heterogeneous disorder that is a challenge for measuring clinical trial efficacy. The current methods of measuring progression of the disease utilizes the Inclusion Body Myositis Functional Rating Scale, grip strength by dynamometer, and finger flexor strength. One of the hallmarks of the disease is selective deep finger flexor weakness. Heretofore, no good data was available to determine how well the Functional Rating Scale relates to this hallmark physical exam deficit. Our study is the first to investigate degree of correlation between items pertaining to hand function in the Functional Rating Scale with measured grip and finger flexor strength in IBM patients. We find lower than expected correlation with finger flexor strength and even less with grip strength. The current Functional Rating Scale will benefit from optimization to better measure clinical progression better.