Calcium / Pentagastrin Test for Calcitonin (CPST)

This test is used to diagnose medullary carcinoma of thyroid.

Protocol

1. Patient should be fasted overnight.
2. Patient should be maintained in supine position.  Insert IV cannula.
3. Take clotted blood for serum calcitonin at 0 min.
4. Infuse 2 mg/kg calcium gluconate over 1 min (10 mL 10% calcium gluconate = 90 mg = 2.25 mmol of calcium) followed immediately by IV pentagastrin 0.5 µg/kg infusion in 5 sec.
5. Check calcitonin levels at 1, 2, 3, 5 and 10 min.

Interpretation

Peak calcitonin level greater than 100 ng/L is diagnostic of medullary carcinoma of thyroid.  For values between 30 – 100 ng/L, the significance is not clear.
 

Precautions

Infusion of calcium may lead to transient sensation of tightness in the pharynx and retrosternal area and epigastric fullness.  Infusion of pentagastrin may lead to transient abdominal cramp, nausea, chest discomfort and flushing.
 

Specimen Requirement