Diagnostic accuracy of preoperative palpation- versus ultrasound-guided thyroid fine needle aspiration cytology: an observational study

Abstract

Background: Thyroid fine needle aspiration (FNA) is the mainstay for diagnosis of malignancy, and is an integral part of current thyroid nodule assessment. The present study analyzes the diagnostic accuracy of palpation-directed versus ultrasound guided fine-needle aspiration in patients who underwent surgery for thyroid nodules.

Methods: A retrospective chart review of all consecutive patients who had FNA biopsy (palpation or ultrasound guided) of thyroid nodules and underwent thyroid gland surgery between 1998 and 2014 was conducted. The FNA findings of the palpation-guided and ultrasound-guided groups were compared for baseline characteristics. Moreover, the diagnostic accuracy of FNA findings and surgical histopathology results were analyzed.

Results: A total of 1174 patients were included in the study with a mean age of 46.3 ± 11.7 years and the majority were females (75.5%). Among the study population, 392 (33.4%) patients underwent US-guided FNA; 570 (48.6%) had palpation-guided FNA in clinic and no FNA was done in 212 (18%) cases. Patients underwent US-guided FNA were more likely to have suspicion of malignancy (p = 0.001), and had indeterminate findings (p = 0.001). On the other hand, palpation-guided FNA group had significantly higher frequency of benign cytology (p = 0.001). With respect to the suspicion for malignancy as well as malignancy, the US-guided group had a similar diagnostic accuracy in comparison to the palpation group. The proportion of malignancy finding on US-guided FNA (8.9%) was higher than the palpation-guided FNA (6.4%) that had been confirmed on postoperative histopathological examination (p = 0.95).

Conclusion: The present study demonstrates higher sensitivity of US-guided thyroid FNA biopsies over palpation-guided FNA for the suspicion of malignancy; however, the accuracy is comparable. Moreover, both groups showed more postoperative malignancy in the benign and unsatisfactory categories than predicted in the Bethesda system. Further prospective studies are needed to underpin a realistic correlation between FNA and final histopathology reports.

Keywords: Diagnostic accuracy; malignancy; palpation and ultrasound-guided FNAC; thyroid surgery.