Objective To investigate the influence of ultrasound characteristics of thyroid nodules on the inefficiency of ultrasound-guided fine-needle aspiration（US-FNA）.Methods A total of 235 cases of thyroid nodules（251 nodules） with malignant risk were selected from our hospital.They were grouped according to their conventional ultrasound characteristics（nodule size

depth

type of calcification

proportion of calcification and proportion of solidity）.All were examined by US-FNA and the inefficiency of specimens was judged according to the classification standard of Bethesda（Bethesda class Ⅰ was invalid and Bethesda≥Ⅱ was valid）.The inefficiencies of various types of groups were compared

and the impact of relevant ultrasound characteristics on the inefficiency was analyzed.Results US-FNA inefficiency comparison:①grouped by nodules size:group A1（0.5 cm≤Maximum diameter<l cm） with the highest inefficiency of 42.4%.②grouped by nodules depth

group C2（deep level） with the highest inefficiency of 41.9%.③grouped by calcification type

group C3（coarse calcification） with the highest inefficiency of 49.1%.④grouped by calcification ratio（C-R）

the inefficiency of US-FNA were 75.0% and 80.0% in D4 group（50%<C-R≤75%） and E4 group（75%<C-R）.⑤grouped by solid ratio（S-R）

the inefficiency of US-FNA were 83.3% and80.0% in A5 group（0<S-R≤25%） and B5 group（25%<S-R≤50%）.Compared with the other groups in the corresponding feature category

the above inefficiency groups had statistically significant differences（all P<0.05）.Conclusion The size of thyroid nodules are small（0.5 cm≤Maximum diameter<1.0 cm）

the located deep

eoarse calcification

calcification ratio C-R>50%

solid ratio S-R≤50%

will cause the unsatisfactory results of US-FNA to some extent.