Intraoperative determination of PTH concentrations in fine needle tissue aspirates to identify parathyroid tissue during parathyroidectomy.

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.