Thursday, February 10, 2011

Q & A: PTH Assay Not Currently Available: Alternatives for Workup of Hypercalcemia?

I have a 12 year, F/S, Shih Tzu with hypercalcemia. A tumor search (lymph node aspirates, rectal exam, chest and abdominal radiographs) have revealed nothing so far. I sent a PTH, iCa, to the Michigan State Endocrine Laboratory (part of the Diagnostic Center for Population and Animal Health). After two weeks of waiting, I just received notification that the lab can't run the PTH due to unavailability of the reagents and may not be able to run the test for several weeks.

Are there any alternatives to confirming the diagnosis of primary hyperparathyroidism? Are there other veterinary laboratories that run PTH?

My Response:

The only other thing to consider diagnostically while waiting for the PTH result would be cervical ultrasound by an experienced sonographer armed with the proper transducer. If a large parathyroid mass mass is identified, that would be pretty decent presumptive evidence of primary hyperparathyroidism

If you haven't already done so, I'd repeat the total calcium and confirm the hypercalcemia by also measuring an ionized calcium. It is possible to have a high total calcium with a normal ionized calcium value. If that's the case, it's probably nothing to worry about. If the dog ill or showing any renal compromise? If the dog is stable, I'd just be patient. There's usually no need to rush to treatment if the underlying cause of the hypercalcemia is a parathyroid tumor.

We just got notification from the Michigan State Endocrine Laboratory that they received the PTH reagents and that all back ordered test results would be available soon. So the good news is the the PTH assay is back up and running. See the link below for more information.

It turns out that all of the commercial laboratories (Antech and Idexx), as well as most (if not all of the veterinary labs (e.g., Cornell, CSU, UC-Davis, Minnesota, Auburn, and Tennessee) all send their PTH samples to the Michigan State Endocrine Laboratory.

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