Quantitative muscle ultrasound and electrical impedance myography in late onset Pompe disease: A pilot study of reliability, longitudinal change and correlation with function.

BACKGROUND/OBJECTIVES: Late-onset Pompe disease (LOPD) is slowly progressive, making it difficult to assess clinical change and response to interventions. In this study, quantitative muscle ultrasonography (QMUS) and electrical impedance myography (EIM) were evaluated as potential biomarkers. METHODS: 25 patients with confirmed LOPD were recruited from the Duke Pompe Clinic and evaluated with standard clinical measures, QMUS, standard EIM (sEIM) and hand-held EIM (hEIM). Patients were evaluated at baseline, 12 months and 24 months. MUS, sEIM and hEIM were compared with the clinical data. Five patients were given hEIM devices to perform measurements at home. RESULTS: QMUS and hEIM had good reliability as measures of muscle structure and conduction properties. Home, patient-performed hEIM measurements did not differ significantly from those performed in the clinic setting. Thirteen patients completed all follow-up measures. Most measures did not change over the study period, however, vastus lateralis echointensity increased 27%, a sign of declining muscle health. Additionally, significant correlations between QMUS, hEIM and measures of muscle strength and function were present. CONCLUSIONS: QMUS and hEIM may provide useful outcome measures for future studies in LOPD with hEIM providing an opportunity to collect data at home. Larger, multicenter studies are needed to explore these possibilities.

Point of Care Quantitative Assessment of Muscle Health in Older Individuals: An Investigation of Quantitative Muscle Ultrasound and Electrical Impedance Myography Techniques.

Background: Muscle health is recognized for its critical role in the functionality and well-being of older adults. Readily accessible, reliable, and inexpensive methods of measuring muscle health are needed to advance research and clinical care. Methods: In this prospective, blinded study, 27 patients underwent quantitative muscle ultrasound (QMUS), standard electrical impedance myography (sEIM), and handheld electrical impedance myography (hEIM) of the anterior thigh musculature by two independent examiners. Subjects also had dual-energy X-ray absorptiometry (DEXA) scans and standardized tests of physical function and strength. Data were analyzed for intra- and inter-rater reliability, along with correlations with DEXA and physical measures. Results: Measures of intra- and inter-rater reliability were excellent (>0.90) for all QMUS, sEIM, and hEIM parameters except intra-rater reliability of rectus femoris echointensity (0.87-0.89). There were moderate, inverse correlations between QMUS, sEIM, and hEIM parameters and measures of knee extensor strength. Moderate to strong correlations (0.57-0.81) were noted between investigational measures and DEXA-measured fat mass. Conclusions: QMUS, sEIM and hEIM were highly reliable in a controlled, same-day testing protocol. Multiple correlations with measures of strength and body composition were noted for each method. Point-of-care technologies may provide an alternative means of measuring health.