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.