Assessing the accuracy of neuromuscular ultrasound for inclusion body myositis.

INTRODUCTION: Inclusion body myositis (IBM) can have clinical and electrodiagnostic features similar to other neuromuscular diseases, making it a diagnostic challenge. This prospective study was designed to determine the accuracy of forearm ultrasound for IBM.

METHODS: Sixty adults were recruited (15 with IBM, 15 with amyotrophic lateral sclerosis [ALS], 15 with other myopathies, and 15 healthy controls), and each underwent ultrasound of the bilateral forearms (imaging the flexor digitorum profundus and flexor carpi ulnaris muscles). Three clinicians with varying ultrasound expertise assigned a diagnosis of IBM, ALS, other myopathy, or control, based on images alone.

RESULTS: Intrarater reliability was moderately strong. Interrater reliability varied based on clinician experience. Sensitivity was 73.33% and 66.67% for the expert raters. Specificity was strong for all 3 clinicians (93.33%, 84.44%, and 91.11%).

DISCUSSION: Neuromuscular ultrasound of the forearm is reliable and accurate for the diagnosis of IBM, although sensitivity was higher among experienced clinicians. Muscle Nerve 59:478-481, 2019.