541P Comparative evaluation of pulmonary function tests and self-reported respiratory function in inclusion body myositis based on NT5c1A antibody serology status.

Inclusion body myositis (IBM) is the most common acquired muscle disease found in individuals over the age of 40. Affected individuals experience a progressive and asymmetric weakness that affects mobility and daily activities. Respiratory failure is a common outcome for IBM patients. Previous analysis in small cohorts of IBM patients has shown subjects who are seropositive for NT5c1A antibody demonstrate significantly lower results in pulmonary function testing (specifically maximum inspiratory pressure (MIP) and forced vital capacity (FVC)), thus predicting more severe respiratory involvement. However, further analysis on pulmonary function and seropositivity for NT5c1A antibody in a larger cohort is needed. A 13-center observational prospective study is ongoing involving 150 patients with IBM (INSPIRE-IBM study). We analyzed data collected at the Baseline visit which includes objective pulmonary function tests (sitting and supine FVC, MIP, and MEP) and a self-reported dyspnea questionnaire (NIHPROMIS dyspnea) and compared the association with seropositivity for NT51A antibodies. Results show the mean seated FVC values were 73.6% predicted in seropositive patients versus 88.2% predicted in seronegative patients (p= 0.005). The mean supine FVC values were 71.6% predicted in seropositive patients versus 84.4% predicted in seronegative patients (p= 0.003). Both are statistically significant. The mean MIP and MEP values (58.4, 75.5 cmH2O seropositive and 65.3, 87.1 cmH2O seronegative) trend lower in seropositive patients but were not clinically significant. The PROMIS dyspnea results showed no significant difference between the two groups. These findings amongst a large cohort of IBM patients, support previous studies showing seropositive IBM patients may have more severe respiratory involvement. [ABSTRACT FROM AUTHOR]