The diagnostic efficiency of ultrasound in characterization for thyroid nodules: how many criteria are required to predict malignancy?

Objective: The purpose of this study was to define the criteria for use in differentiating benign and malignant nodules with the help of the receiver operating characteristic analysis and to increase the objective diagnostic accuracy of ultrasonography. Materials and methods: A total of 363 patients (307 women, 56 men) with 363 nodules (22 malignant and 341 benign nodules) were included in the study. The presence and absence of each US feature of the evaluated nodule - shape taller than wide, irregular margin, hypoechogenicity, microcalcification, and intranodular vascularity - were scored 1 and 0, respectively. The total ultrasound score was obtained by the summing up of each positive ultrasound findings for malignancy. The effect of the total US score in the discrimination of benign and malignant nodules was analysed using ROC analysis. Results: The cut off values of US score at maximum sensitivity and specificity for nodules larger and smaller than one centimeter were two (Az: 0.783) and three (Az: 0.935), respectively. For nodules greater than one centimeter, the calculated diagnostic performances including sensitivity, specificity, positive predictive value and negative predictive value, and accuracy were 62.5%, 91.5%, 30.3%, 97.7%, and 89.9%, respectively. For nodules smaller or equal to one centimeter; the sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 83.3%, 94.9%, 62.5%, 98.2% and 93.8%, respectively. Conclusion: Using ultraound, thyroid nodules can be characterized effectively. The number of the US features used in this distinction varies in respect to the nodule size.