Validation of a chemiluminescent parathyroid hormone assay and intraoperative and postoperative chemiluminescent parathyroid hormone monitoring in dogs undergoing parathyroidectomy for primary hyperparathyroidism

Purpose

The purpose of this study is to evaluate a rapid chemiluminescent test that measures parathyroid hormone, PTH. Our goal is to validate this rapid point of care assay to improve cure rates in canine patients undergoing parathyroidectomy for PHPTH and with postoperative monitoring determine patients that are at a higher risk of developing hypocalcemia, establishing guidelines for calcium supplementation in dogs.

Background

Primary hyperparathyroidism occurs when single or multiple parathyroid glands become hyperfunctional and secrete excessive intact parathyroid hormone (PTH), resulting in the development of hypercalcemia. Surgical excision of all hyperfunctional tissue is curative and rapid intraoperative PTH assays have become standard of care in people with PHPTH undergoing parathyroidectomy to confirm excision of the hyperfunctional tissue. A preliminary study has described similar findings in dogs.

The ADVIA Centaur Intact PTH assay (ioPTH) measures intact PTH concentrations and is used for routine and perioperative monitoring of PTH in people with primary hyperparathyroidism (PHPTH). This is a chemiluminescent assay which provides PTH concentrations within 30 minutes compared to the standard immunoradiometric assay which requires sending to the specimen to an outside lab and waiting 1-2 weeks for the result. We hypothesize that this assay can be used to measure canine PTH, that perioperative PTH monitoring will confirm excision of hyperfunctional tissue, and that documentation of increasing PTH concentrations will correspond with normalization of ionized calcium concentrations.

Persistent hypercalcemia causes suppression of the unaffected parathyroid glands; therefore the most common complication in dogs following parathyroidectomy is hypocalcemia. The current method of assessing a dog following surgery is to monitor ionized calcium levels, which doesn’t provide information about the function of the remaining parathyroid glands. As a result, dogs remain hospitalized for ongoing calcium monitoring and are supplemented with vitamin D analogs and calcium. There is paucity in the literature regarding dogs that are at a high risk of developing hypocalcemia, those developing sustained hypocalcemia, and there are no guidelines for supplementation. Monitoring PTH concentrations will provide a more accurate assessment of parathyroid gland function allowing patients to leave the hospital sooner, provide insight as to the mechanism of sustained hypocalcemia, and allow the clinician to more accurately provide vitamin D and calcium supplementation.

Inclusion Criteria:

To qualify for enrollment in this study, dogs must have:

  • A standard work-up to diagnose primary hyperparathyroidism

  • OR Dogs that are over 8 years old and clinically normal

Study Design

Patients and their records will be reviewed to confirm documentation of PHPTH diagnosis, and if incomplete the remaining diagnostic tests will be performed. Patients will be treated with the standard of care for PHPTH by undergoing general anesthesia and surgical removal of abnormal parathyroid gland(s). Patients will have an additional 3ml of blood collected prior to surgery and after surgery. All patients recover in the ICU and ionized calcium concentrations will be monitored every 12 hours until normalization of ionized calcium. Patients will have an additional 2ml of blood collected at each calcium recheck for PTH monitoring. Follow-up visits to recheck ionized calcium and PTH occur 14 days and 3 months following surgery.

Clinically normal dogs will have a physical exam and 4ml of blood collected once.

Client Cost

  • Client is responsible for all routine costs associated with surgery, but is not responsible for PTH monitoring and follow-up visits.

Client Contact

Jennifer Song
Small animal surgery resident
614-292-3551
song [dot] 628 [at] osu [dot] edu or

Kathleen Ham
Assistant Professor small animal surgery
ham [dot] 61 [at] osu [dot] edu
614-292-3551