Bhaskar Roy1, Seward B Rutkove2, Richard J Nowak3. 1. Yale School of Medicine, Department of Neurology, 15 York Street, LCI 9, P.O. Box 208108, New Haven, CT 06519, USA. Electronic address: bhaskar.roy@yale.edu. 2. Beth Israel Deaconess Medical Center, Department of Neurology, 330 Brookline Ave, Boston, MA 02215, USA. Electronic address: srutkove@bidmc.harvard.edu. 3. Yale School of Medicine, Department of Neurology, 15 York Street, LCI 9, P.O. Box 208108, New Haven, CT 06519, USA. Electronic address: richard.nowak@yale.edu.
Abstract
OBJECTIVE: To assess the value of electrical impedance myography (EIM) in inclusion body myositis (IBM). METHODS: Patients with clinically defined IBM and healthy controls (HC) of similar age group were recruited. Each participant underwent manual muscle testing (MMT), 6-min walk test (6MWT), handgrip dynamometry, and IBM-functional rating scale assessment (IBM-FRS). EIM measurements were obtained from bilateral deltoid, biceps, forearm-flexors, quadriceps, tibialis anterior, and medial gastrocnemius. RESULTS: Fourteen IBM patients and 12 HCs with mean age 68.6 ± 6 and 67.4 ± 5.4 years were included in the final analysis. Averaged phase value at 50 kHz (EIM50) and ratio of phase value at 50 kHz/200 kHz (EIMPR) from six-muscles were significantly lower in IBM patients when compared to HC (5.23 ± 1.34 vs 7.88 ± 1.9, p-value 0.002, and 0.55 ± 0.09 vs. 0.68 ± 0.09, p-value 0.004, respectively). A strong correlation was noted between IBM-FRS, 6MWT, disease-duration and the averaged value of EIM50 and EIMPR in the IBM patients (Spearman |rho|>0.7, p-values < 0.01). CONCLUSIONS: EIM can differentiate between IBM patients and HCs and EIM parameters correlate with clinical outcome measures. SIGNIFICANCE: EIM may be a potential objective biomarker for IBM. A longitudinal validation study is warranted.
OBJECTIVE: To assess the value of electrical impedance myography (EIM) in inclusion body myositis (IBM). METHODS:Patients with clinically defined IBM and healthy controls (HC) of similar age group were recruited. Each participant underwent manual muscle testing (MMT), 6-min walk test (6MWT), handgrip dynamometry, and IBM-functional rating scale assessment (IBM-FRS). EIM measurements were obtained from bilateral deltoid, biceps, forearm-flexors, quadriceps, tibialis anterior, and medial gastrocnemius. RESULTS: Fourteen IBM patients and 12 HCs with mean age 68.6 ± 6 and 67.4 ± 5.4 years were included in the final analysis. Averaged phase value at 50 kHz (EIM50) and ratio of phase value at 50 kHz/200 kHz (EIMPR) from six-muscles were significantly lower in IBM patients when compared to HC (5.23 ± 1.34 vs 7.88 ± 1.9, p-value 0.002, and 0.55 ± 0.09 vs. 0.68 ± 0.09, p-value 0.004, respectively). A strong correlation was noted between IBM-FRS, 6MWT, disease-duration and the averaged value of EIM50 and EIMPR in the IBM patients (Spearman |rho|>0.7, p-values < 0.01). CONCLUSIONS: EIM can differentiate between IBM patients and HCs and EIM parameters correlate with clinical outcome measures. SIGNIFICANCE: EIM may be a potential objective biomarker for IBM. A longitudinal validation study is warranted.