Objective: To assess the clinical application value of fine-needle aspiration (FNA) plus assaying parathyroid hormone (PTH) in the washing liquid of FNA samples for identification of parathyroid gland during thyroidectomy. 
Methods: Thirty-one patients undergoing thyroid surgery during December 2014 to May 2015 were enrolled. During operation, FNA was performed and the nature of the tissues (parathyroid gland, thyroid gland, muscle, fat, lymph node and thymus) of FNA samples was judged by naked eye, and then, the PTH levels in the washing liquid of the aspirated tissues were measured and the corresponding tissues were sent for pathological examination simultaneously. The PTH levels in the washing liquid from different aspirated tissues were compared, and the sensitivity and specificity of measurement of PTH in the tissue washing liquid for identification of parathyroid gland were analyzed.
Results: A total of 186 FNA samples were obtained, including 28 parathyroid and 158 non-parathyroid tissues. The average concentration of PTH was 1431.83 (214–5 000) pg/mL for parathyroid, 20.26 (10.36–30.57) pg/mL for thyroid, 22.26 (13.38–31.24) pg/mL for muscle, 22.51 (13.25–29.83) pg/mL for fat, and 20.67 (10.23–
31.60) pg/mL for lymph node. The concentration of PTH in parathyroid tissue was significantly higher than those in non-parathyroid tissues (all P<0.001), which showed no significant differences among the non-parathyroid tissues (P>0.05). Both sensitivity and specificity of the concentration of PTH in the tissue washing liquid >37.92 pg/mL
were 100% for identification of parathyroid tissue. No permanent hypoparathyroidism occurred in any of the patients undergoing FNA.
Conclusion: Determination of PTH in the washing liquid of FNA samples is a reliable, safe, and simple method for discrimination of parathyroid and non-parathyroid tissue during thyroidectomy.