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

AIM: 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.

METHODS: 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 non-conservative method. The threshold for statistical performance was set at 0.05. Each sonographic feature was also compared with its pathology results.

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.

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