Objective: To assess the diagnostic value of ultrasound-guided fine needle aspiration (US-FNA) cytological examination for thyroid nodules and the influential factors.
Methods: The clinical data of patients with thyroid nodules (2 380 nodules) undergoing thyroidectomy between January 2016 and December 2018 were retrospectively analyzed. Using the postoperative pathological results as reference standard, the diagnostic efficiency of US-FNA for thyroid nodules was calculated, and the influences of ultrasound features and nodule size on the diagnosis were also analyzed.
Results: Among the 2 380 nodules, 133 were diagnosed as benign nodule (Bethesda II) and 1 468 were diagnosed as malignant nodule (Bethesda VI), in which 1 534 were consistent with the pathological results. The overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of US-FNA in diagnosis of thyroid nodules were 98.0% (95% CI=97.3%–98.7%), 73.2% (95% CI=65.9%–80.5%), 97.4% (95% CI=96.6%–98.2%), 78.2% (95% CI=71.2%–85.2%) and 95.8% (95% CI=94.8%–96.8%), respectively. Both false positive and false negative rates of US-FNA diagnosis for thyroid nodules with diameter ≤10 mm were higher than for those with diameter >10 mm, and the false negative rates of US-FNA diagnosis for thyroid nodules with ultrasound appearance of absence of microcalcification or vascular flow were increased, while the false positive rate of US-FNA diagnosis for hypoechoic nodules was increased (all P<0.05).
Conclusion: US-FNA is of high value in the differential diagnosis of thyroid nodules, and it is easy to operate and less traumatic, so it deserves to be widely used. However, the false positive and negative results should be taken into account in nodules with diameter >10 mm or nodules without microcalcification or vascular flow as well as the hypoechoic nodules.