FrançaisHow IMHA is diagnosed
The ACVIM consensus statement states that there is no gold standard test. A firm diagnosis needs an anemia, at least 2 markers of immune destruction (or agglutination that persists after washing) and at least 1 sign of hemolysis. With fewer criteria the diagnosis is “supportive” or “suspicious”, provided no other cause of anemia is found [1].
| Test | What it shows | To know |
|---|---|---|
| Spherocytes on the blood smear | Small round red cells that have lost part of their membrane to antibodies. | At ≥5 per oil field: 63% sensitivity and 95% specificity. Also seen with zinc, some toxins, snake bites and some cancers [1]. |
| Saline agglutination test | Red cells clump together even when diluted with saline. | 1 drop of blood with 4 drops of saline has very high specificity; washing helps in doubtful cases [1]. |
| Coombs test (DAT) | Antibodies attached to the red cells. | Sensitivity 61–82%, specificity 94–100%; ideally sampled before treatment or transfusion [1]. |
| Bilirubin, plasma and urine | Signs of red cell destruction: jaundice, high bilirubin, red plasma or urine, ghost cells. | Liver disease and sample damage must be excluded [1]. |
How to read the hematocrit line
Here is an example line from a dog with IMHA.
- Abbreviation HCT or PCV: the share of the blood made up of red cells.
- Result 14% in this illustrative line: a severe anemia.
- Unit Percent, or L/L (0.14).
- Laboratory interval An illustrative dog interval; each laboratory sets its own.
- Flag L: below the interval. In IMHA, a spun PCV is preferred, because clumping can make the analyser’s value unreliable [1].
A non-regenerative picture does not rule IMHA out: about 30% of dogs have a non-regenerative anemia when first seen [1], partly because the marrow needs 3 to 5 days to respond [2]. See anemia in dogs.
Looking for a trigger
- Infections: Babesia (strongest evidence), plus tests for Anaplasma, Ehrlichia, Bartonella, heartworm and, in endemic areas, Leishmania [1]. See tick-borne diseases in dogs.
- Zinc: abdominal X-rays look for swallowed coins or metal objects [1].
- Drugs and vaccines: drug causes are rare; no conclusive link has been shown with vaccines, and current vaccination strategies are considered generally safe [1].
- Cancer: no causal link has been shown, but it cannot be excluded; screening is at the vet’s discretion [1].
The minimum work-up also includes a blood smear read by a clinical pathologist, a chemistry panel and a urinalysis [1].
Blood clots: the main danger
The treatment consensus describes blood clots, especially in the lungs, as a leading cause of illness and death in IMHA. The risk is higher with red cell destruction inside the vessels, clumping, a very high white cell count and high liver enzymes. Anti-clotting treatment is recommended for nearly all dogs, and the highest risk of death is in the first 2 weeks of treatment [3].
Related articles
En français : l’anémie hémolytique du chien.
Questions to ask your veterinarian
- Which IMHA criteria does my dog meet: spherocytes, agglutination, Coombs test?
- Is the anemia regenerative, and how severe is it?
- Which infections and other triggers should we test for?
- Is my dog at risk of blood clots, and how is that managed?
- How often will we recheck the hematocrit?
Get your dog’s blood count explained, line by line.
AI DiagAnimals reads the hematocrit, reticulocytes, platelets, bilirubin and the rest of the panel together with your laboratory’s intervals, and prepares the questions for your vet. The service opens soon: leave your email to be told first.
Frequently asked questions
What is a Coombs test in dogs?
A test that detects antibodies attached to the red cells. It supports IMHA, but it is positive in only 61–82% of affected dogs [1].
What is an autoagglutination test used for?
It checks whether red cells clump together when mixed with saline, a marker of antibodies on the red cells. Washing the cells helps tell true clumping from stacking (rouleaux) [1].
What are the underlying causes of IMHA?
Often no cause is found. Vets look for triggers such as Babesia and other infections, zinc, drugs and cancer [1].
What is the life expectancy of a dog with IMHA?
IMHA is serious, and the first 2 weeks carry the highest risk, mainly from blood clots. Dogs that get through this period usually need several months of treatment and regular blood checks [3].
Can vaccines cause IMHA?
No conclusive link has been shown, and the consensus considers current vaccination strategies generally safe [1].
Sources
- Garden OA et al. ACVIM consensus statement on the diagnosis of immune-mediated hemolytic anemia in dogs and cats. J Vet Intern Med. 2019;33(2):313-334. doi.org/10.1111/jvim.15441
- eClinPath, Cornell University College of Veterinary Medicine. Assessment of regeneration. eclinpath.com/hematology/anemia/assessment-regeneration
- Swann JW et al. ACVIM consensus statement on the treatment of immune-mediated hemolytic anemia in dogs. J Vet Intern Med. 2019;33(3):1141-1172. doi.org/10.1111/jvim.15463
Laboratory methods and reference intervals vary. This article explains; it does not diagnose. For a decision about your pet, use the original report and talk to your veterinarian. Our editorial policy.