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ACTH Stimulation (One Pre, One Post)
Canine/Feline Baseline cortisol, one post-ACTH cortisol
Suggested Protocol: Collect 3 mL of blood. Centrifuge and separate at least 1 mL of serum for a resting cortisol for all of the following protocols. Label the tubes with the patient's last name and either "pre", "post 30 minutes", "post one hour" or "post two hours".
Canine- Repository corticotropin (ACTH Gel; 40 IU/mL):
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Administer ACTH gel, 1 IU/lb (2.2 IU/kg) IM (maximum total dose 40 IU).
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Collect 1 mL of serum one and two hours after injection for post-cortisols (use Test Code 125 to submit three time points). A single post sample drawn at two hours may also be acceptable.
Canine-Synthetic aqueous ACTH (generic cosyntropin, Cortosyn®* or Synacthen®* [non-depot form]; 0.25 mg/mL):
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Administer one vial (0.25 mg) of synthetic ACTH IV (generic cosyntropin) or IM, regardless of the dog's size. Alternatively, administer 5 ug/kg of synthetic ACTH (Cortrosyn® or Synacthen® only) IV or IM. Consider the ug/kg protocol in smaller dogs.
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Collect 1 mL of serum one hour after injection for a post-cortisol.
Canine-Tetracosactrin zinc phosphate (Synacthen Depot) ®; 1 mg/mL):
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Administer 0.5 mg (1/2 vial) for patients < 15 kg, or 1 mg (1 vial) for patients >15 kg IM. Note: do NOT administer Synacthen Depot® IV.
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Collect 1 mL of serum one hour after injection for a post-cortisol
Feline- ACTH Gel:
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Administer ACTH gel, 1 IU/lb IM (maximum total dose 40 IU)
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Collect 1 mL of serum one and two hours after injection for post-cortisols (use Test Code 125 to submit three time points).
Feline-Synthetic aqueous ACTH (generic cosyntropin, Cortosyn®* or Synacthen®* [non-depot form]; 0.25 mg/mL):
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Administer 0.125 mg (1/2 vial) of synthetic ACTH IV (generic cosyntropin) or IM. Alternatively, administer 5 ug/kg of synthetic ACTH (Cortosyn® or Synacthen® only) IV.
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Collect 1 mL of serum 30 minutes and 60 minutes after injection for post-cortisols (use Test Code 125 to submit three time points).
Feline- Repository corticotropin (ACTH Gel; 40 IU/mL):
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Administer ACTH gel, 1 IU/lb (2.2 IU/kg) IM
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Collect 1 mL of serum one and two hours after injection for post-cortisols (use Test Code 125 to submit three time points)
Feline- Tetracosactrin zinc phosphate (Synacthen Depot 1 mg/mL):
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Administer 0.5 mg (1/2 vial) IM. Note: do NOT administer Synacthen Depot® IV
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Collect 1 mL of serum 30 minutes and 60 minutes after injection for post-cortisols (use Test Code 125 to submit three time points)
*Cortrosyn® and Synacthen®: after reconstitution, the remainder of the vial may be aliquoted and frozen for future use. Aliquot the Cortosyn® or Synacthen® into plastic syringes and store in a non-frost-free freezer for up to 6 months. Do not allow syringe to thaw other than right before administration.
Hyperadrenocorticism Lysodren® therapy monitoring protocol:
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Induction phase ACTH response test- to document response to therapy and mark the end of the induction phase, perform the test every five to seven days or sooner, depending on clinical signs. Maintenance therapy should begin when the pre- and post-cortisol concentrations are between 1 and 5 ug/dL.
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Maintenance therapy monitoring- an ACTH response test should be repeated after the first month of maintenance therapy and every two to three months thereafter for proper treatment supervision and dose adjustment. If dose adjustment is required, a recheck ACTH stimulation is recommended one month after every change in dose.
Hyperadrenocorticism trilostane (Vetoryl®)therapy monitoring protocol:
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Ten days after initiating therapy, perform an ACTH stimulation test. The test should be performed 4-6 hours post-Trilostane administration. Goals for therapy are pre- and post- cortisol concentrations between 1.5 and6 ug/dL. Alternatively, the manufacturer has suggested that pre-and post- cortisol concentrationsof 6-9ug/dL (testing performed 4 hours post-Trilostane)are acceptable if clinical signs have resolved. If dose adjustment is required, a recheck ACTH stimulation is recommended 10-14 days after every change in dose.
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Recheck ACTH stimulation tests should be repeated after the first month of maintenance therapy and every two to three months thereafter for proper treatment supervision and dose adjustment.
Results:
Canine:
Pre-ACTH (resting) cortisol: 2-6 μg/dL
Post-ACTH cortisol: 6-18 μg/dL
Equivocal post-ACTH cortisol: 18-22 μg/dL
Post-ACTH cortisol consistent with hyperadrenocorticism: >22 μg/dL
Post-ACTH cortisol consistent with hypoadrenocorticism: <2 μg/dL
Desired pre- and post-ACTH cortisol on Lysodren® therapy: 1-5 μg/dL
Desired pre- and post-ACTH cortisol on trilostane* therapy: 1.5-6 μg/dL
The ACTH response test is only clearly positive (>22 μg/dL) in 30% of dogs with hyperadrenocorticism (HAC), and normal in 40% of dogs with HAC. If the ACTH response test is normal and HAC is still suspected, proceed with a low-dose dexamethasone suppression test.
Dogs with iatrogenic Cushing's syndrome will have flatline response test results in the low end or below the normal reference range.
*Recommendations for target cortisol levels on trilostane (Vetoryl®) therapy vary. Per the manufacturer, pre- and post-ACTH cortisol levels of 6-9 μg/dL (testing performed 4 hours post-trilostane) may be sufficient for some animals if clinical signs are well controlled.
Feline:
Pre-ACTH (resting) cortisol: 0.5-5 μg/dL
Post-ACTH cortisol: 5-15 μg/dL
Equivocal post-ACTH cortisol: 15-19 μg/dL
Post-ACTH cortisol consistent with hyperadrenocorticisim: >19 μg/dL
Post-ACTH cortisol consistent with hypoadrenocorticism: <0.5 μg/dL
Both hyper- and hypoadrenocorticism are rare diseases in cats.
Canine and feline low-dose dexamethasone suppression test:
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Collect 1 mL of serum for a baseline cortisol and label the tube with "pre-dex" and the patient's name.
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Administer dexamethasone, 0.01 mg/kg IV (preferred) or IM. Dexamethasone sodium phosphate (Azium-SP™) or dexamethasone in polyethylene glycol (Azium™) can be used.
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Collect a second blood sample eight hours post-injection. Label tube with the applicable hours post-dexamethasone injection and the patient's name.
Canine and feline high-dose dexamethasone suppression test:
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Collect 1 mL of serum for a baseline cortisol and label the tube with "pre-dex" and the patient's name.
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Administer dexamethasone, 0.1 mg/kg IV (preferred) or IM. Dexamethasone sodium phosphate (Azium-SP™) or dexamethasone in polyethylene glycol (Azium™) can be used.
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Collect a second blood sample eight hours post-injection. Label tube with the applicable hours post-dexamethasone injection and the patient's name.
Low-Dose Dexamethasone Diagnostic Intervals (Canine):
Results
|
4 hours (μg/dL) |
8 hours (µg/dL) |
Interpretation |
|---|---|---|
| <1 | <1 | Normal |
| 1.0-1.5 | 1.0-1.5 | Inconclusive |
| >1.5 and >50% of basal cortisol concentration | >1.5 and >50% of basal cortisol concentration | Consistent with hyperadrenocorticism, further testing required to differentiate adrenal tumor from pituitary-dependent hyperadrenocorticism (PDH) |
| <1.5 or <50% of basal cortisol concentration | >1.5 and >50% of basal cortisol concentration | Consistent with pituitary-dependent hyperadrenocorticism (PDH) |
| <1.5 or <50% of basal cortisol concentration | >1.5 but <50% of basal cortisol concentration | Consistent with pituitary-dependent hyperadrenocorticism (PDH) |
| >1.5 and >50% of basal cortisol concentration | >1.5 but <50% of basal cortisol concentration | Consistent with pituitary-dependent hyperadrenocorticism (PDH) |
Hyperadrenocorticism is a clinical disorder with clinical signs. If the animal has no clinical signs, we do not recommend treatment. Approximately 5% of dogs with hyperadrenocorticism will have normal low dose dexamethasone suppression results. Conversely, some animals with significant nonadrenal disease may fail to adequately suppress on this test.
High-Dose Dexamethasone Diagnostic Intervals (Canine):
|
4 hours (μg/dL) |
8 hours (µg/dL) |
Interpretation |
|---|---|---|
| <1.5 or <50% of basal cortisol concentration | >1.5 and >50% of basal cortisol concentration | Consistent with pituitary-dependent hyperadrenocorticism (PDH) |
| >1.5 and >50% of basal cortisol concentration | <1.5 or <50% of basal cortisol concentration | Consistent with pituitary-dependent hyperadrenocorticism (PDH) |
| <1.5 or <50% of basal cortisol concentration | <1.5 or <50% of basal cortisol concentration | Consistent with pituitary-dependent hyperadrenocorticism (PDH) |
| >1.5 and >50% of basal cortisol concentration | >1.5 and >50% of basal cortisol concentration | Further testing needed to differentiate PDH from adrenal tumor |
A first morning urine sample obtained in the home environment is recommended.
<34 Hyperadrenocorticism is highly unlikely and investigation of other causes of the dog's clinical signs is recommended.
> or = 34 Hyperadrenocorticism is possible; however a urine sample collected from a stressed dog or dog with nonadrenal illness can have an increased ratio. The urinary cortisol:creatinine ratio is not a specific test for hyperadrenocorticism, and should not be considered a sole diagnostic test for this condition. Addtional testing using either a low-dose dexamethasone suppression test or ACTH stimulation test is recommended for further identification of hyperadrenocorticism.
UPC should be performed only on urine specimens that have an inactive sediment and are free of gross hematuria (color not red or pink). Criteria for an inactive sediment include: white blood cells ≤ 5/hpf, red blood cells < 100 hpf and absence of bacteriuria.
Renal proteinuria (Canine):
UPC < 0.2 non-proteinuric
UPC 0.2-0.5 borderline proteinuric
UPC > 0.5 proteinuric
Renal proteinuria (Feline):
UPC < 0.2 non-proteinuric
UPC 0.2-0.4 borderline proteinuric
UPC > 0.4 proteinuric
The urine protein:creatinine ration (UPC) should be interpreted along with a concurrrent urinalysis. Pre-renal and post-renal proteinuria need to be ruled out prior to evaluating renal proteinuria. Renal proteinuria requires proof of persistence by repeating UPC on at least three urine samples collected over a period of at least 2 weeks.
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Pre-renal proteinuria is possible when a CBC and a biochemical profile detect hemolysis, hyperglobulinemia or evidence of muscle damange. Recommend investigation and management for the underlying cause.
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Post-renal proteinuria is caused by urogenital tract diseases, hematuria or pyuria. Repeat the test with a cystocentesis sample or evaluate urine sediment for hemorrhage or inflammation. Consider a urine culture. Recommend investigation and management for the underlying cause.
Patients with persistent proteinuria in the borderline proteinuric subcategory should be re-evaluated within 2 months and re-classified as appropriate.
If UPC > 0.2 (borderline proteinuric or proteinuric), investigate for underlying systemic disease including inflammatory, infectious or neoplastic conditions. Evaluation for systemic hypertension and azotemia is also recommended.
Consider treating proteinuric patients (dogs UPC > 0.5; cats UPC > 0.4) according to the International Renal Interest Society (IRIS) guidelines on proteinuria.
For more detailed information on investigation and management of proteinuria, renal staging and treatment algorithms visit www.iris-kidney.com.
Canine/Feline Preprandial 0.0-6.9 μmol/L
Postprandial 0.0-14.9 μmol/L
Elevated pre or post-prandial bile acids are suggestive of decreased liver function, but do not indicate the nature of the abnormality or whether the problem is reversible or permanent. Normal bile acids do not rule out the presence of hepatic disease. Mild elevations (15-30) may also be seen with extrahepatic disease (e.g. small intestinal bacterial overgrowth [SIBO], hyperadrenocorticism, etc.) If clinical signs and other diganostic findings are suggestive of primary liver disease, consider additional diagnostics to further evaluate the liver, including repeat bile acids panel in 2 to 4 weeks. Moderate to severe elevations (>30) are consistent with hepatic dysfunction, but cannot discriminate specific liver diseases or the relative severity of liver disease. Additional diagnostics (e.g. ultrasound and/or liver biopsy) are recommended to further classify the disease process.
Note: if the serum bilirubin concentration is elevated or the animal is icteric, there is little additional diagnostic value in performing the bile acids test.
Test Protocol
- Fast the dog or cat approximately 12 hours and obtain a fasting (preprandial) serum specimen of at least 1 mL. Label the tube "fasting" or "preprandial".
- Ideally, feed the animal a high-fat meal to stimulate gallbladder contraction. The minimum amount of food is 2 tsp for small patients (<10 lb) and 2 Tbsp for large patients. If encephalopathic effects of protein are anticipated, use a restricted-protein food mixed with a small amount of corn oil.
- Two hours after feeding, obtain a postprandial serum specimen of at least 1 mL, and label the tube "postprandial".
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