Convergent validity and test-retest reliability of multimodal ultrasound and related clinical measures in people with chronic stroke.

Abstract Objective To assess the test-retest reliability of diagnostic ultrasound measurements of the bilateral biceps brachii (BB), brachial artery, medial gastrocnemius (MG) and popliteal artery in stroke survivors and their convergent validity with related clinical comparators. Design This was a cross-sectional study. Setting All procedures were conducted in a university laboratory. Participants Sixty-five community dwelling adults (26 women, 39 men) with an average age of 60.9±7.7 years and stroke duration of 5.7±3.9 years participated in this study. Interventions Not applicable. Main Outcome Measures Measures of muscle structure (i.e., thickness, cross-sectional area, fascicle length and pennation angle), stiffness and intramuscular blood perfusion were conducted using B-mode, elastography and color flow Doppler ultrasound modes, respectively. Convergent validity was assessed by examining correlations between ultrasound measures and assessments of related constructs [i.e., dynamic stiffness, isometric peak torque, spasticity and systemic vascular function using myotonometry, dynamometry, the Composite Spasticity Scale (CSS) and the Ankle-Brachial Index (ABI), respectively]. A two-way random-effects intraclass correlation coefficient model (ICC2,3) was used to determine agreement between intersession measures among a smaller cohort of participants with stroke (n=20). Results ICC estimates ranged from moderate to excellent for muscle stiffness (paretic: ICC=0.74-0.89; non-paretic: ICC=0.66-0.88), structure (paretic: ICC=0.87-0.99; non-paretic: ICC=0.81-0.98) and blood perfusion measures (paretic: ICC=0.74-0.84; non-paretic: ICC=0.73-0.88). Weak to moderate associations were found between myotonometry and elastography measures of the bilateral BB (r=0.29-0.52, p≤0.05) and MG muscles (r=0.31-0.69, p≤0.05). The correlations between elastography measures and spasticity scores for the paretic upper (r=0.35-0.63, p≤0.05) and lower limbs (r=0.25-0.37, p≤0.05) were also weak to moderate. Conclusions Elastography demonstrated mostly weak to moderate correlation with measures of stiffness using myotonometry as well as scores of paretic upper and lower limb spasticity. The results also indicate acceptable intersession reliability for muscle and vascular measures using several ultrasound modalities among individuals with chronic stroke.