Pattern-based vs. score-based guidelines using ultrasound features have different strengths in risk stratification of thyroid nodules

Objective: To evaluate and compare the diagnostic performances between recently published pattern-based and score-based TIRADS according to the experience level of the performer. Methods: From July 2013 to January 2019, 8657 thyroid nodules in 8364 patients that had been cytopathologically diagnosed as benign or malignant were included (mean size, 22.0 mm ± 12.1). Thyroid nodules were categorized into US-based final assessment categories and US-FNA indications of five recently published TIRADS. Radiologists performing the US examinations were divided into the experienced vs. inexperienced group. Diagnostic performances and unnecessary biopsy rates were calculated and compared between the five TIRADS, also the experienced vs. inexperienced group. Results: Of the 8657 thyroid nodules, 6706 (77.5%) were benign and 1951 (22.5%) were malignant. Diagnostic performances for US-based final assessment categories showed higher sensitivity and NPV for EU-TIRADS (92.7% and 96.5%), while Kwak-TIRADS had higher specificity, PPV, accuracy, and AUC (89.6%, 68.0%, 86.5%, and 0.878; all p < 0.05, respectively). Diagnostic performances for US-FNA indications showed higher sensitivity and NPV for KTA/KSThR TIRADS (98.5% and 97.0%), while Kwak-TIRADS had higher specificity, PPV, accuracy, and AUC (70.3%, 46.6%, 74.5%, and 0.797; all p < 0.05, respectively). Unnecessary biopsy rates were the lowest in Kwak-TIRADS for both US categories and US-FNA indications (32.0% and 53.4%, p < 0.001). Similar trends were seen in both the experienced and inexperienced group. Conclusion: The currently published score-based guidelines for thyroid nodules have significantly higher specificity, PPV, accuracy, and AUC and lower unnecessary biopsy rates, whereas pattern-based guidelines have higher sensitivity and NPV, regardless of the level of experience of the performer. Key Points: • For US-based final assessment categories, EU-TIRADS had higher sensitivity and NPV, while Kwak-TIRADS had higher specificity, PPV, accuracy, and AUC. • For US-FNA indications, KTA/KSThR TIRADS had higher sensitivity and NPV, while Kwak-TIRADS had higher specificity, PPV, accuracy, and AUC. • Similar trends were seen in diagnostic performances for both experienced and inexperienced groups.