Reliability of the ultrasound classification system of thyroid nodules in predicting malignancy

This study aims to evaluate the reliability of the Ultrasound (U) Classification system in predicting thyroid malignancy by using pathology diagnosis as the reference standard.

It was a cross sectional study carried out at Universiti Kebangsaan Malaysia Medical Centre (UKMMC), Malaysia. Records of patients with focal thyroid nodules on ultrasound (US) for which US guided fine needle aspiration cytology (FNAC) was performed and pathology results were available, from January 2014 to May 2016 were selected for review. Correlation of the U Classification with pathology results was assessed. Sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, predictive value, negative predictive value and accuracy were calculated in a conservative and nonconservative method. The threshold for statistical performance was set at 0.05. Each sonographic feature was also compared with its pathology results.

A total of 91 patients with 104 nodules were eligible. 12 nodules out of 104 (11.5%) were malignant. The sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, positive predictive value, negative predictive value and accuracy were 100%, 91.3%, 11.5, 0.0, 60%, 100% and 92.3%, and 100%, 91.4%, 11.7, 0.0, 78.6%, 100% and 93.5%, for the non-conservative and conservative method of calculations respectively.

The U Classification is reliable in predicting thyroid malignancy. More evidence is nevertheless necessary for widespread adaptation and use.