PARATHYROID HORMONE (PTH) AND IONISED CALCIUM (iCa) ASSAYS

Combination of PTH and iCa measurements can help distinguish between:

  1. PRIMARY HYPERPARATHYROIDISM (parathyroid dependent hypercalcaemia) – functional parathyroid neoplasia.
  2. PARATHYROID SUPPRESSION (parathyroid independent hypercalcaemia) – hypercalcaemia of malignancy, vitamin D toxicosis (cholecalciferol rodenticide), feline idiopathic hypercalcaemia.
  3. PRIMARY HYPOPARATHYROIDISM (parathyroid dependent hypocalcaemia) – parathyroid destruction by inflammation or surgery.
  4. SECONDARY HYPERPARATHYROIDISM (parathyroid independent hypocalcaemia) – renal failure, calcium losses (eg pancreatitis), dietary deficiency, hyperadrenocorticism, hyperthyroidism.

SAMPLE REQUIREMENTS FOR PARATHYROID HORMONE ASSAY

This test requires at least 1ml EDTA plasma collected on ice and rapidly frozen.

  1. Place the blood sample into a cooled plastic (NOT glass) EDTA tube kept on ice.
  2. Mix well but gently and centrifuge as quickly as possible – ideally in a refrigerated centrifuge.
  3. Transfer the plasma supernatant into a cooled plastic (NOT glass) PLAIN tube kept on ice.
  4. LABEL “PTH” and freeze the EDTA plasma sample immediately and KEEP FROZEN OVERNIGHT before collection by the BattLab courier who will bring a transport freezer pack – please call the lab to let us know this is a sample requiring special handling.

SAMPLE REQUIREMENTS FOR IONISED CALCIUM ASSAY

This test requires at least 200ul of separated serum collected under anaerobic conditions.

  1. 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.
  2. 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.
  3. LABEL “CALCIUM” and REFRIGERATE (DO NOT FREEZE) the anaerobic serum sample before collection by the BattLab courier – please call the lab to let us know this is a sample requiring special handling.
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