Diagnostic Accuracy of Ultrasonography in Classifying Thyroid Nodules Compared with Fine-Needle Aspiration

Classifying thyroid lesions is challenging; nonetheless, using ultrasonography may allow for accurate diagnosis, differentiation and management of thyroid lesions and help avoid unnecessary biopsy.

The main objective of the study is to determine the diagnostic accuracy of ultrasonography in classifying thyroid nodules compared with fine-needle aspiration.

This retrospective study included all 68 patients diagnosed with thyroid nodules at King Fahd Hospital of the University, Al Khobar, Saudi Arabia, between June 1, 2014, and November 30, 2016. Parameters were selected based on the Society of Radiologists in Ultrasound criteria. Ultrasonographic features, namely, nodule margins, echotexture, vascularity and calcifications, and fine-needle aspiration cytology (FNAC) results were reviewed by two radiologists blinded to each other's findings and validated by another experienced interventional radiologist. Ultrasonography results were compared against that of FNAC to calculate sensitivity and positive- and negative-likelihood ratios, and the nodule types were compared using Fisher's exact test.

Of the 68 nodules analyzed, 59 were reported as benign using FNAC (specificity = 95%; P < 0.001). Of these 59, 56 were also reported as benign using ultrasonography. The specificity of ultrasonography in determining benign nodules was 94.9%, and the positive- and negative-likelihood ratios were 13.0 and 0.35, respectively. Six of the nine suspicious nodules were confirmed as malignant using FNAC, and the ultrasonography and FNAC findings were strongly associated (P = 0.001). According to the Society of Radiologists in Ultrasound criteria, FNAC and ultrasonography findings were significantly associated for nodule calcification (P = 0.001) and echogenicity (P = 0.001).

The diagnostic specificity of ultrasonography and FNAC in this study are consistent with those reported previously, indicating that ultrasonography reliably classifies thyroid nodules, and thus can assist in the decision-making regarding need for biopsy.