Positive predictive value and interobserver variability of preoperative staging sonography for thyroid carcinoma

Abstract

OBJECTIVE: The purpose of this article is to evaluate the positive predictive value (PPV) and interobserver variability of preoperative staging sonography for thyroid carcinoma.

SUBJECTS AND METHODS: Eighty-five patients (median age, 45 years) were included. The T and N staging were classified according to TNM classification. Extrathyroidal extension was defined as contact with the capsule greater than 25% of the perimeter of a malignant lesion or loss of the capsule line. The sonography criteria for lymph node metastases were absence of echogenic fatty hilum, round shape, hyperechogenicity, microcalcifications, cystic change, and peripheral vascularity. The PPV and interobserver variability of two radiologists were calculated.

RESULTS: The mean size of 85 malignancies was 8.6 mm, with 17 that were larger than 10 mm and 68 that were 10 mm or smaller. PPV ranges of sonography by two radiologists were 65-100% for T staging, 44.4-45.5% for multifocality, 71.4-81.8% for bilaterality, 28.6-80% for N1a staging, and 40-100% for N1b staging. In all malignancies, the kappa values were 0.5319 for T staging, 0.7741 for multifocality, 0.8604 for bilaterality, and 0.6793 for N staging. In 17 malignancies larger than 10 mm, the corresponding kappa values were lower (κ = 0.4516, 0.5952, 0.8211, and 0.6364, respectively). In 68 malignancies 10 mm or smaller, the corresponding kappa values showed slight improvements, except for T staging (κ = 0.5016, 0.8413, 0.8721, and 0.6821, respectively).

CONCLUSION: The T staging, bilaterality, and N1b staging of preoperative staging sonography showed high PPV. Agreements for T and N staging, multifocality, and bilaterality were moderate, substantial, substantial, and excellent, respectively.