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 nodul es 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 ran dom to sample the nodules. For each nodule, four passes were performed in random order, two with 23-gauge needles and two with 27-gauge need les. If a specific pass yielded no tissue or blood, as determined by v isual inspection (i.e., the sample was dry), the procedure was repeate d until a satisfactory sample was obtained. After each patient had lef t the department, the aspirates were reviewed by a cytopathologist (wh o was not aware of needle size or operator identity) to determine diag nostic adequacy. RESULTS: Among the 123 nodules, 88 were solid, and 35 were complex cysts. There was no significant difference between the t wo sizes of needle in the adequacy of the samples obtained (102 nodule s 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 si gnificantly fewer dry passes with the larger needle (2 with the 23-gau ge needle and 16 with the 27-gauge needle; chi(2) test, p = 0.0022). S ixteen nodules were inadequately sampled with both needles. Eight of t hese were less than 1 cm in greatest dimension. Only one solid nodule greater than 1 cm in greatest dimension was inadequately sampled. Ther e was no difference in yield among the three radiologists (chi(2) test , p = 0.5192). No significant complications were encountered. CONCLUSI ONS: Needles of both 23 and 27 gauge can be used to obtain fine-needle aspiration biopsy samples from thyroid nodules. Using both sizes is r ecommended, 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 aspira tion biopsy with equal proficiency.