Validation of a rapid parathyroid hormone assay and intraoperative measurement of parathyroid hormone in dogs with benign naturally occurring primary hyperparathyroidism.

Objectives: To (1) validate a rapid chemiluminescent parathyroid hormone (PTH) assay, (2) determine it's usefulness locating a parathyroid nodule(s), and (3) determine if >50% decrease in PTH corresponds with excision of autonomously functioning parathyroid tissue.

Study Design: Prospective cohort study.

Animals: Dogs (n=12) with naturally occurring primary hyperparathyroidism and 25 healthy dogs.

Methods: The assay was validated with linearity, precision, and intermethod comparison. Preoperative and postoperative systemic plasma PTH concentrations, measured from saphenous venous blood, were compared. Intraoperative local PTH concentrations were measured in right and left jugular venous blood before and after surgical excision of the grossly abnormal parathyroid gland(s).

Results: Within run and day-to-day precisions were acceptable (coefficient of variation <15%). Dilutional parallelism was used to demonstrate high correlation between measured and calculated PTH concentrations (R(2)=0.99). The assay methods had good correlation but numerical results of the rapid assay were usually lower than the immunoradiometric assay. Seven of 12 dogs had uniglandular disease and five had multiglandular disease. Systemic and local PTH concentrations decreased >50% in all the dogs after excision of the parathyroid gland(s). Mean preoperative systemic plasma PTH concentrations were significantly higher than mean postoperative systemic concentrations. Local PTH concentrations could not be used reliably to differentiate the side of the autonomously functioning gland(s). Hypercalcemia resolved postoperatively in all the dogs.

Conclusion: This assay measures PTH in dogs. Rapid PTH measurement provided documentation of decreased PTH concentration after removal of autonomously functioning parathyroid tissue.

Clinical Relevance: Use of this assay allows documentation of a significant decrease in PTH concentration after excision of autonomously functioning parathyroid tissue.