Introduction: Muscle biopsy is commonly used to diagnose inflammatory myopathies. We evaluated the ability of muscle ultrasound, a non-invasive and simple tool, to distinguish between healthy subjects and patients with inflammatory myopathy.
Methods: This study was conducted on 17 patients recently diagnosed with biopsy inflammatory myopathies (12 dermatomyositis, 5 polymyositis) compared with 17 age- and gender-matched healthy control adults. All patients underwent clinical assessments, including manual muscle testing, hand-held dynamometry, and muscle ultrasound evaluations, including thickness and echo intensity in predefined muscle groups.
Results: The disease duration was seven months (interquartile range: 3 to 11 months). Except for the biceps and gastrocnemius, patients' muscles had significantly higher echo intensity and lower thickness than the control group. The echo intensity sum-score manifested the highest area under the curve compared to the sum-scores of other variables (echo intensity vs manual muscle testing: Area under curves-difference=0.18, P<0.01; echo intensity vs dynamometry: Area under curves-difference=0.14, P=0.02; echo intensity vs thickness: Area under curves-differences-difference=0.25, P<0.01).
Conclusion: The echo intensity of muscles differed significantly between healthy individuals and patients with inflammatory myopathies and may serve as a useful diagnostic biomarker.
Keywords: Case-control studies; Myositis; Sensitivity and specificity; Ultrasonography.
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