PTH, PTHrP, Vitamin D and iCa measurements can help distinguish between:
PRIMARY HYPERPARATHYROIDIS
(parathyroid dependent hypercalcaemia) – functional parathyroid neoplasia
PARATHYROID SUPPRESSIO
(parathyroid independent hypercalcaemia) – hypercalcaemia of malignancy, vitamin D toxicosis (cholecalciferol rodenticide), feline idiopathic hypercalcaemia
PRIMARY HYPOPARATHYROIDISM
(parathyroid dependent hypocalcaemia) – parathyroid destruction by inflammation or surgery
SECONDARY HYPERPARATHYROIDISM
(parathyroid independent hypocalcaemia) – renal failure, calcium losses (ie. pancreatitis), dietary deficiency, hyperadrenocorticism, hyperthyroidism
SAMPLE REQUIREMENTS FOR PTH and PTHrP ASSAYS
These tests require at least 1ml separated EDTA plasma collected on ice and rapidly frozen. Ionised calcium should be measured concurrently.
- Place the blood sample into a cooled plastic (NOT glass) EDTA tube kept on ice.
- Mix well but gently and centrifuge as quickly as possible – ideally in a refrigerated centrifuge.
- Transfer the plasma supernatant into a cooled plastic (NOT glass) plain tube kept on ice.
- Label “PTH” and/or “PTHrP” and freeze the EDTA plasma sample immediately and keep frozen overnight before collection by:
SAMPLE REQUIREMENTS FOR IONISED CALCIUM ASSAY
This test requires at least 200ul of separated serum collected under anaerobic conditions.
- Collect the blood into serum tubes (gel barrier tubes must NOT be used) and ensure that each tube is 100% full – when screwing the lid down, avoid the inclusion of any air bubbles which will destroy the ionised calcium.
- Allow 15 minutes for the blood to clot and then centrifuge at 7,500 g for 5 minutes. Remove the serum and place into another plain tube which must be 100% filled and airtight – ie containing no air bubbles at all.
- Label “CALCIUM” and refrigerate (do not freeze) the anaerobic serum sample before collection by the courier.
SAMPLE REQUIREMENTS FOR VITAMIN D ASSAY
These tests require at least 1ml separated serum rapidly frozen. Ionised calcium should be measured concurrently.
- Place the blood sample into a plastic (NOT glass) plain tube.
- Allow 15 minutes for the blood to clot and then centrifuge at 7,500 g for 5 minutes
- Remove the serum and place into another plain tube.
- Label “VITAMIND D” and freeze the serum sample immediately, protecting it from light, and keep frozen overnight before collection by:
