Assessment of quadriceps muscle thickness using bedside ultrasonography by nurses and physicians in the intensive care unit: Intra- and inter-operator agreement

BACKGROUND: Data regarding the agreement among multiple operators for measurement of quadriceps muscle thickness by bedside ultrasonography (USG) are sparse. AIM: To statistically assess the agreement among 5 operators for measurement of quadriceps muscle thickness on bedside USG. METHODS: This was a cross-sectional observational study. The 5 operators of varied experience (comprised of 1 critical care consultant, 2 fellows, and 2 nurses) independently measured quadriceps muscle thickness in triplicate for 45 critically ill patients each, using USG. Intra- and interrater agreement rates among the 5 operators were assessed using intraclass correlation coefficient (ICC) and expressed with 95% confidence interval (CI). RESULTS: The 5 operators produced a total of 135 readings and 675 observations for ICC calculations to determine the intraoperator and interoperator variations respectively. For intraoperator agreement, the overall ICC (95%CI) was 0.998 (0.997, 0.999) for operator 1, 0.998 (0.997, 0.999) for operator 2, 0.997 (0.995, 0.999) for operator 3, 0.999 (0.998, 0.999) for operator 4, and 0.998 (0.997, 0.999) for operator 5. For interoperator agreement, the overall ICC (95%CI) was 0.977 (0.965, 0.986; P < 0.001) for reading 1, 0.974 (0.960, 0.984; P < 0.001) for reading 2, and 0.975 (0.961, 0.985; P < 0.001) for reading 3. CONCLUSION: USG measurement of quadriceps muscle thickness was not dependent on clinical experience, supporting training for nurses in it.