Implementation of Evidence-Based Guidelines for Thyroid Nodule Biopsy: A Model for Establishment of Practice Standards

Multiple studies have defined criteria for the selection of thyroid nodules for biopsy. No set of criteria is sufficiently sensitive and specific. The aim of this study is to develop a method for assessing consistency of practice in an ultrasound group and to determine whether a 5-point malignancy rating scale can be used to select patients for biopsy. One hundred one nodules (50 benign and 51 malignant) were selected from a thyroid biopsy database. Seven radiologists were educated on evidence-based criteria used to select nodules for biopsy. Using this information, readers graded the likelihood of malignancy using a 5-point malignancy rating scale, where 1 equals the lowest probability of malignancy and 5 equals the highest probability of malignancy, on the basis of overall impression of sonographic findings. Interobserver agreement on biopsy recommendation, reader sensitivity, specificity, and accuracy were determined. The sensitivity and specificity of biopsy recommendation were 96.1% and 52%, respectively. The misclassification rate was 25.7%, and accuracy was 74.3%. Interobserver agreement on biopsy recommendation was fair to substantial (κ, 0.38-0.69). The proportion of agreement was excellent for malignant nodules (0.88-1.0). The risk of malignancy increased with increasing malignancy rating: 4.3% of nodules with a malignancy rating of 1 were malignant versus 93.4% of those assigned a rating of 5. Our study illustrates a method to evaluate the standard of practice for thyroid nodule assessment among radiologists within an ultrasound group. Application of a 5-point malignancy rating scale to select nodules for biopsy is feasible and shows good diagnostic accuracy.