Role of operator experience in ultrasound-guided fine-needle aspiration biopsy of the thyroid

Purpose. Thyroid nodules are commonly encountered in clinical practice, and ultrasound (US)-guided fine-needle aspiration biopsy (FNAB) is the gold standard in diagnosing the pathological nature of undetermined thyroid nodules. The aim of this study was to evaluate whether operator experience influences the diagnostic accuracy of US-guided FNAB. Materials and methods. A total of 700 consecutive US-guided FNAB done by a single radiologist between 2000 and 2007 were retrospectively analysed. The same freehand technique and capillary-action technique with 22-or 25-gauge needles was used for all nodules, All specimens were prepared and fixed without the cytologist on site and were subsequently analysed by two expert cytologists. The procedures were chronologically divided into seven groups and classified as diagnostic or nondiagnostic. Results. The rate of nondiagnostic procedures for each group was 32% in group 1, 13% in group 2, 17% in group 3, 11% in group 4, 10% in group 5, 5% in group 6 and 8% in group 7. No major complications were recorded. Conclusions. The rate of nondiagnostic US-guided FNAB is heavily dependent on the operator's experience. We estimated that at least 200 procedures need to be performed in order to achieve the levels of diagnostic accuracy reported in the literature. We therefore suggest specific training before operators routinely perform this procedure in clinical practice.