Intraobserver and Interobserver Variability in Ultrasound Measurements of Thyroid Nodules

ObjectivesThe purpose of this study was to assess the intraobserver and interobserver variability in ultrasound (US) measurements of thyroid nodules. MethodsWe performed a prospective study of the US examinations of 73 patients with 122 thyroid nodules greater than 5mm in size. Ultrasound measurements in 4 dimensions (anteroposterior, transverse, longitudinal, and maximum diameters) and measurement of the estimated volume (using the ellipsoid formula) of each thyroid nodule were performed twice by 2 independent radiologists (A and B, with 10 years and 6 months of experience, respectively). The intraobserver and interobserver variability in measurements of thyroid nodules was assessed by a Bland-Altman analysis of agreement. The absolute values for intraobserver and interobserver variability were compared by a paired t test. ResultsThe 95% intraobserver and interobserver limits of agreement for the anteroposterior, transverse, longitudinal, and maximum diameters and estimated volume of thyroid nodules were 18.2%,+/- 14.3%, and +/- 21.0%;+/- 17.2%%,+/- 17.3%, and 18.2%;+/- 14.6%,+/- 15.5%, and +/- 22.3%;+/- 13.8%,+/- 15.5%, and +/- 19.6%; and +/- 30.2%,+/- 27.7%, and +/- 44.1%, respectively. The absolute values for intraobserver variability were lower than those for interobserver variability for all measurements. ConclusionsThere was considerable intraobserver and interobserver variability in US measurement of thyroid nodules, which must be taken into account during follow-up US examinations of patients with thyroid nodules.