Needle size and sample adequacy in ultrasound-guided biopsy of thyroid nodules.

OBJECTIVES: To determine the optimal needle size (23-gauge or 27-gauge) for ultrasound-guided fine-needle aspiration biopsy of thyroid nodules and to compare the interoperator yield for this procedure. PATIENTS AND METHOD: Over an 11-month period, 123 patients underwent biopsy of a thyroid nodule. Three experienced radiologists were assigned at random to sample the nodules. For each nodule, four passes were performed in random order, two with 23-gauge needles and two with 27-gauge needles. If a specific pass yielded no tissue or blood, as determined by visual inspection (i.e., the sample was dry), the procedure was repeated until a satisfactory sample was obtained. After each patient had left the department, the aspirates were reviewed by a cytopathologist (who was not aware of needle size or operator identity) to determine diagnostic adequacy. RESULTS: Among the 123 nodules, 88 were solid, and 35 were complex cysts. There was no significant difference between the two sizes of needle in the adequacy of the samples obtained (102 nodules were adequately sampled with the 23-gauge needle and 95 with the 27-gauge needle; McNemar chi 2 test, p = 0.1456). However, there were significantly fewer dry passes with the larger needle (2 with the 23-gauge needle and 16 with the 27-gauge needle; chi 2 test, p = 0.0022). Sixteen nodules were inadequately sampled with both needles. Eight of these were less than 1 cm in greatest dimension. Only one solid nodule greater than 1 cm in greatest dimension was inadequately sampled. There was no difference in yield among the three radiologists (chi 2 test, p = 0.5192). No significant complications were encountered. CONCLUSIONS: Needles of both 23 and 27 gauge can be used to obtain fine-needle aspiration biopsy samples from thyroid nodules. Using both sizes is recommended, because the number of dry passes is lower with the larger needle, but the diagnostic quality of the aspirate may be better with the smaller one. Experienced physicians can perform fine-needle aspiration biopsy with equal proficiency.