Background: Exact tissue identification during parathyroidectomy is essential to successfully cure hyperparathyroidism. PTH level determination from tissue aspirates has been advocated as a "biochemical frozen section" for parathyroid tissue identification. We investigated the sensitivity and specificity of this method in a large cohort of consecutive patients who underwent parathyroidectomy in a tertiary referral center.
Methods: PTH levels of 359 tissue aspirates were measured intraoperatively in 223 consecutive patients from March 2006 to December 2008. Suspected parathyroid and control tissues were aspirated with a standardized technique immediately after their excision. Samples were processed for quick-PTH assay with peripheral blood samples before and after excision. PTH levels from tissue aspirates were correlated with pathological diagnosis. The Mann-Whitney test was used to determine statistical significance (P < 0.05).
Results: A total of 255 parathyroid (196 adenoma, 30 hyperplasia, 4 carcinoma, 25 normal parathyroid) and 104 nonparathyroid tissue (88 thyroid, 16 lymph node, thymus, or fat) aspirates were compared. A highly significant difference was found between PTH levels of parathyroid (8,120 +/- 2,711 pg/ml; interquartile range (IQR): 4,949-9,075) and nonparathyroid (0.8 +/- 9.29 pg/ml; IQR: 0.4-1.4) tissue aspirates (P < 0.005). This test is 100% sensitive and 100% specific to identify parathyroid tissue for values >84 pg/ml. Furthermore, PTH levels of pathological parathyroid aspirates (8,169 +/- 2,597; IQR: 5,634-9,109) were higher than that of normal parathyroid aspirates (4,130 +/- 2,952; IQR: 2,569-8,284; P = 0.0011).
Conclusions: PTH level determination from tissue aspirates is a highly reliable, quick, and simple method to differentiate parathyroid and nonparathyroid tissues during parathyroidectomy. This method can obviate frozen sections in patients undergoing surgery for hyperparathyroidism.