The rate of no-diagnostic procedures and operator experience in ultrasound-guided fine-needle aspiration biopsy of the thyroid nodules

Objective In clinical practice,ultrasound-guided fine-needle aspiration biopsy (US-G FNAB) is the gold standard in diagnosing the pathological nature of undetermined thyroid nodules before operation.Re---sults of FNAB may vary substantially among operators with different skills.The aim of this study is to evaluate whether operator experience in US-G FNAB influences the rate of diagnostic procedures.Methods A total of 600 consecutive US-guided FNAB done by a single radiologist with 22-or 27-gauge needles from Feb.2008 to Apr.2012 were retrospectively analyzed.All specimens were prepared and fixed without the cytologist on site and were subsequently analyzed by 2 expert cytologists.The procedures were chronologically divided into 6 groups and further stratified according to the overall (A),solid nodules (B),mixed nodules (C),pure cystic nodules (D),acellular sample(E),heavily blood-stained sample(F),exclusively colloid material(G),incorrect slide fixation(H) and they were classified as diagnostic or no-diagnostic.Results The rate of no-diagnostic procedures for each group in learning curves were reported as:① Among A,34％ in group 1,15％ in group 2,18％in group 3,10％ in group 4,7％ in group 5,and 8％ in group 6.② Among B,4％ in group 1,1％ in group 2,0％ in group 3,0％ in group 4,0％ in group 5,and 0％ in group 6.② Among C,10％ in group 1,1％ in group 2,4％ in group 3,0％ in group 4,1％ in group 5,and 0％ in group 6.④ Among D,20％ in group 1,13％ in group 2,14％ in group 3,10％ in group 4,6％ in group 5,and 8％ in group 6.⑤ Among E,25％ in group 1,15％ in group 2,15％ in group 3,10％ in group 4,6％ in group 5,and 8％ in group 6.⑥ Among F,4％ in group 1,0％ in group 2,1％ in group 3,0％ in group 4,0％ in group 5,and 0％ in group 6.⑦ Among G,1％ in group 1,0％ in group 2,1％ in group 3,0％ in group 4,1％ in group 5,and 0％ in group 6.⑧ Among H,4％ in group 1,0％ in group 2,1％ in group 3,0％ in group 4,0％ in group 5,and 0％ in group 6.Among the 600 procedures,there were 2 cases of vertigo and 4 cases of moderate bleeding at the biopsy site,all of which resolved spontaneously.No major complications were recorded.Conclusions The rate of no-diagnostic US-guided FNAB is heavily dependent on the operator's experience.We estimate that at least 200 procedures are needed in order to achieve the levels of diagnostic accuracy reported in the literature.We therefore suggest operators to get specific training before routinely perform this procedure in clinical practice. Key words: Thyroid nodule;  Fine needle aspiration biopsy;  Ultrasound;  Learning curve