Specimen: EDTA plasma
- Collect an EDTA blood sample any time of the day.
- The sample must be chilled within 3 hours of collection, preferably immediately after collection.
- If possible separate the plasma from the red cell pack. This can be done by centrifugation or by allowing gravity to sediment the red cells.
- Freeze the separated plasma and send to the lab with gel ice packs.
- If separation is not possible, wrap the chilled EDTA sample lightly in cotton wool and send with gel ice packs. NOTE it is very important that unseparated samples do not become frozen as the resulting haemolysis will invalidate the test results. Also do not freeze the plasma if the separation was done by gravity sedimentation.
Special handling/shipping requirements: Yes, see above.
General information about when this test is indicated:
Endogenous ACTH has largely superseded the overnight dexamethasone suppression test as the screening test of choice for the diagnosis of pituitary pars intermedia dysfunction (PPID, also known as equine Cushing’s syndrome). Testing can be performed at any time of the year although test performance is highest in the autumn. Both non-PPID and PPID horses display higher ACTH concentrations in the autumn (March, April, May) compared with other times of the year but the response is more exaggerated in PPID horses. A seasonal reference interval appropriate for the time of year must be used. The same test can be used in donkeys.