Value of Repeated Fine Needle Aspirations of the Thyroid: An Analysis of Over Ten Thousand FNAs

Objective: Fine needle aspiration (FNA) has been accepted as the diagnostic method of choice in the initial evaluation of thyroid nodules. However, the value of repeated FNAs in the long-term follow-up of lesions initially diagnosed as benign is being questioned. Do the findings on initial FNA really spare patients thyroidectomy or do they only postpone it? The purpose of the present study is our attempt to answer this question. Design: Retrospective review of cytology reports of patients who underwent thyroidal FNAs at Washington Hospital Center from January 1998 through April 2006. All statistical analyses were done using the statistical package Splus. Main outcome: Patients who had thyroid nodules diagnosed as benign on FNA performed at our institution had a 90% probability of a benign diagnosis (with 95% confidence interval [0.87, 0.92]), when they underwent surgery. When the benign cytologic diagnosis was confirmed on a repeat aspiration, this probability increased to 98% (with 95% confidence interval [0.94, 1.0]). Conclusions: Repeated thyroidal FNAs yielding benign diagnoses are nearly always accurate (98%), and therefore the patients can be followed safely without undergoing surgery, unless an unfavorable clinical change occurs.