Intra- and Inter-observer Reliability of Quadriceps Muscle Thickness Measured with Bedside Ultrasonography by Critical Care Physicians

BACKGROUND: Muscle wasting is common among critically ill patients with sepsis and has a significant effect on clinical outcome. However, appropriate tool for measurement of muscle loss is debatable. Ultrasonography (USG) has been used for objective assessment of quadriceps muscle thickness among these patients; however, there is limited data on its reliability. AIMS AND OBJECTIVE: This study was aimed to assess the reliability of quadriceps muscle thickness as measured by critical care physicians. METHODOLOGY: This cross-sectional study included twenty patients with sepsis. Quadriceps muscle thickness was measured on right mid-thigh at a predefined point by two critical care fellows using bedside USG. Intra- and inter-observer reliability of the measurements was assessed by intra-class correlation coefficient (ICC). RESULTS: Hundred and twenty quadriceps muscle thickness measurements, three by each of the two critical care fellows, were done in twenty patients with sepsis. First, second, and third measurements (mean ± standard deviation) taken by the first observer (RK) were 35.030 ± 3.546 mm, 35.055 ± 3.307 mm, and 35.245 ± 3.027 mm, respectively. The three values recorded by the second observer (AD) were 35.585 ± 3.746 mm, 35.1 ± 3.006 mm, and 34.89 ± 2.556 mm, respectively. ICC for observer 1 and 2 was 0.925 (95% confidence interval [CI]: 0.851–0.967) and 0.835 (95% CI: 0.689–0.925), respectively. The mean difference of measurement between two observers was 0.082 mm (95% CI: −1.194–1.031). The mean ICC (95% CI) for inter-observer reliability was 0.992 (0.979–0.997); P < 0.001. CONCLUSIONS: This study shows that ultrasound is a reliable tool for the measurement of quadriceps muscle thickness by critical care physicians with excellent inter- and intra-class reliability.