Table 5. Unnecessary FNA rates of the 2020 C-TIRADS, 2017 ACR-TIRADS and 2015 ATA guidelines.
| Guidelines | Nodules for recommending FNA (n) | Benign nodules (n) | Unnecessary FNA rate (%) | P value |
|---|---|---|---|---|
| Total | ||||
| C-TIRADS | 632 | 386 | 61.08 | <0.001* |
| ACR-TIRADS | 702 | 534 | 76.07 | 0.006** |
| ATA guidelines | 995 | 812 | 81.61 | <0.001*** |
| <20 mm | ||||
| C-TIRADS | 309 | 121 | 39.16 | 0.15* |
| ACR-TIRADS | 158 | 51 | 32.28 | <0.001** |
| ATA guidelines | 260 | 141 | 54.23 | <0.001*** |
| ≥20 mm | ||||
| C-TIRADS | 323 | 265 | 82.04 | 0.005*; <0.001**** |
| ACR-TIRADS | 544 | 483 | 88.79 | 0.14**; <0.001**** |
| ATA guidelines | 735 | 671 | 91.29 | <0.001***; <0.001**** |
The P value reflects the difference in the unnecessary FNA rate: *, between C-TIRADS and ACR-TIRADS; **, between ACR-TIRADS and ATA; ***, between C-TIRADS and ATA; ****, between the two subgroups based on the same guidelines. The unnecessary FNA rates were calculated using the following equation: unnecessary FNA rate = the number of benign nodules among the recommended FNA nodules/the number of recommended FNA nodules. C-TIRADS, Chinese Thyroid Imaging Reporting and Data System; ACR-TIRADS, Thyroid Imaging Reporting and Data System of the American College of Radiology; ATA guidelines, American Thyroid Association guidelines; FNA, fine needle aspiration.