Utilizing CT Based Imaging Parameters of Body Composition to Understand Heterogeneity of Response to Biologic Therapies in Severe Asthma Cohorts

Muscle size was measured as the skeletal muscle cross-sectional area in centimeters squared (cm2) measured at the level of the T10 vertebra to determine the cutoff value in chest wall muscle size that optimally classified patients that had and did not have any reduction in pre-treatment baseline exacerbation frequency (binary).

Muscle quality was measured as the skeletal muscle density in Hounsfield Units (HU) to determine the cutoff value in chest wall muscle quality that optimally classified patients that had and did not have any reduction in pre-treatment baseline exacerbation frequency (binary).

Muscle size was measured as the skeletal muscle cross-sectional area in centimeters squared (cm2) measured at the level of the T10 vertebra to assess whether skeletal muscle size area could be used to predict exacerbation frequency. Results reflect the average muscle sizes when frequency could be predicted.

Muscle quality was measured as the skeletal muscle density in Hounsfield Units (HU) to determine the cutoff value in chest wall muscle quality to assess whether skeletal muscle quality could be used to predict exacerbation frequency. Results reflect the average muscle sizes when frequency could be predicted.

The number of exacerbations post-biologic were compared to the the number of baseline exacerbations. Baseline measurements were counted in the year prior to biologic initiation. Any exacerbation recorded between 4 to 28 months after biologic initiation was recorded as a post-biologic exacerbation. Any reduction in between the pre- and post-biologic was counted as an exacerbation reduction. Results reflect the number of participants who experienced (True) or did not experience (False) a reduction in exacerbations.

Muscle size was used to investigate body composition measures associated with a 5% or greater improvement in forced expiratory volume in one second (FEV1). Muscle size was measured as the skeletal muscle cross-sectional area in centimeters squared (cm2) measured at the level of the T10 vertebra to determine the cutoff value in chest wall muscle size that optimally classified participants who had and did not have improvement in FEV1. Participants with ≥5% improvement in FEV1 during the 4 to 18-month period following initiation of biologics were classified as responders. Any participant who did not achieve a ≥5% improvement from baseline in that timeframe was classified as a non-responder.

Muscle size was used to investigate body composition measures associated with any reduction in maintenance OCS use when compared to baseline OCS use. Subjects with any OCS reduction in use during the 4- to 18-month period following initiation of biologics were classified as responders.