ObjectiveTo assess the effect of short-axis and long-axis punctures of thyroid nodules on the diagnostic rate of ultrasound guided aspiration biopsy (US-FNAB). MethodsWe retrospectively analyzed the clinical data of 2 686 thyroid nodule patients who underwent US-FNAB between March 2011 and November 2014. The US-FNAB was performed by 5 beginners (571 each for Dr1-Dr4 and 402 for Dr5). Yields of US-FNAB were divided into two levels according to the classification standard of the Bethesda system:adequacy and inadequacy. Short-axis puncture technique was used by Dr2 and long-axis puncture was performed by the others. According to chronological sequence of thyroid nodules examined, we compared the inadequate diagnostic rate between Dr2 and the others for the first 200 cases and the last 200 cases, respectively. The inadequate diagnostic rate was compared among the 4 doctors who used long-axis punctures for the first 200 cases and the last 200 cases, respectively. ResultsThe inadequacy rate of US-FNAB for Dr2 was higher than that for Dr1, Dr3, Dr4 and Dr5 in the first 200 cases, with statistical significance (P=0.036,<0.001,=0.007 and <0.001, respectively). There was no significant difference in inadequate diagnostic rate among the 4 doctors who used long-axis punctures for the first 200 cases (P=0.033, 0.551, 0.011, 0.122, 0.672 and 0.050). The inadequacy rate of US-FNAB for Dr2 was higher than that for Dr5 and lower than that for Dr4 in the last 200 cases with statistical significance (P=0.027 and 0.003, respectively). The inadequacy rate of US-FNAB for Dr5 was lower than that for Dr3 (P=0.005) and Dr4 (P<0.001) among the 4 doctors who used long-axis punctures for the last 200 cases. ConclusionFor beginners, the inadequacy rate of short-axis puncture is higher than long-axis puncture. We suggest beginners learn long-axis puncture method. There is no significant difference in inadequate diagnostic rate among short-axis and long-axis punctures, when the number of operated cases reaches 200. At this point, the operator can choose either way to puncture according to the disease condition or personal interests.