Objective: Ultrasound-guided fine-needle aspiration biopsy (US-FNAB) is a safe and effective method for screening malignant thyroid nodules. The purpose of this study was to compare the diagnostic effectiveness of US-FNAB for nodules of different sizes.
Methods: A total of 1085 patients with thyroid nodules who underwent US-FNAB between January 2021 and July 2023 were included in the study. The patients were divided into three groups based on the maximum diameter of the nodules: there were 324 patients with thyroid nodules ≤ 5 mm in Group A, 537 patients with thyroid nodules between 6 mm and 10 mm in Group B, and 224 patients with thyroid nodules > 10 mm in Group C. The US-FNAB satisfactory specimen rate, biopsy time and cytopathological results for the three groups were collected and compared with the postoperative pathological results.
Results: The US-FNAB satisfactory specimen rates for Groups A, B and C were 84.57% (274/324), 90.13% (484/537) and 94.64% (212/224), respectively. The average biopsy times for Groups A, B, and C were 100.84 ± 41.58 s, 91.20 ± 32.53 s, and 79.01 ± 29.62 s, respectively. In Groups A, B, and C, 103, 192 and 73 patients, respectively, underwent surgery, and the malignancy rates were 88.35%, 85.42% and 72.6%, respectively. The sensitivity, specificity, positive predictive value, and negative predictive value of US-FNAB in Group A were 78.26%, 81.82%, 97.30%, 31.03%; respectively; those in Group B were 73.78%,85.71%,96.80%, and 35.82%, respectively; and those in Group C were 75.47%, 85.00%, 93.02% and 56.67%, respectively.
Conclusion: The US-FNAB satisfactory specimen rate for thyroid nodules ≤ 5 mm was relatively low, but the size of nodules had no effect on the diagnostic sensitivity of US-FNAB; additionally, nodules ≤ 5 mm had a higher probability of malignancy. Therefore, it is necessary to perform US-FNAB for thyroid nodules with a diameter ≤ 5 mm with malignant signs.

Keywords: thyroid nodules, ultrasound-guided fine-needle aspiration biopsy, microcarcinomas