Intra- and inter-rater reliability of biceps thickness assessment by ultrasound in elderly

Rationale: Although ultrasound has been reported as valid and reliable tool to assess muscle size in older adults1, little is known about intra-rater reliability (intra-RR) and inter-rater reliability (inter-RR) of BodyMetrix in specific to assess small muscles. Therefore, in this study we aimed to assess intra-RR and inter-RR of biceps muscle size (thickness) in elderly.Methods: Thirty elderly (81.9±6.3 years; 80% women; BMI 26.7±5.3 kg/m2) living in a Portuguese nursing home/residence were included. To assess procedural intra-RR and inter-RR, ultrasound measurements were performed by two raters (R1, R2, beginners level) by BodyMetrixTM BX2000, on the biceps of the right arm. R1 repeated the ultrasound measurement once. To assess measurement intra-RR and inter-RR, images were analyzed by three raters (R1, R2, and R3 [experienced level]). Agreement was analyzed by intraclass correlation coefficient. ICC values of 0.50 to 0.75 were considered moderate to good, and >0.75 as good to excellent. Statistical significance was set at p<0.05.Results: Mean muscle thickness at 1st and 2nd measurement (R1) was 23.4±4.5 and 23.7±3.8 mm, respectively. For procedural intra-RR, ICC was 0.630. For inter-RR of image 1 (R1) vs. image 2 (R2), ICC was 0.622. For inter-RR of image 2 (R2) vs. image 3 (R1) ICC was 0.534. For measurement reliability, ICCs for intra-RR of R1 and R2 were 0.865 and 0.766, respectively. ICCs for inter-RR of R1 vs. R2, R2 vs. R3, and R1 vs. R3 were 0.865, 0.800, and 0.815, respectively. All ICCs were statistically significant (p≤0.001).Conclusion: The results of our study indicate that procedural reliability of biceps muscle size as assessed by BodyMetrix in elderly is moderate to good, and measurement reliability is good to excellent. Increasing the level of experience may further improve procedural reliability.