Electrical impedance myography as a biomarker of inclusion body myositis: A cross-sectional study.

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.