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reactions and cold-reactive IgM are more likely to be associated with secondary disease.
The chances of a false-negative Coombs test are minimized by performing the complete test as described above. However, it is possible for rare cases to have insufficient RBC-associated immunoreactants for detection or for circulating RBCs to be unaffected
where the immune attack is directed against erythroid precursors in the bone marrow (non-regenerative IMHA or pure red cell aplasia).
In some laboratories, detection of RBC-bound immunoreactants is performed using fluorochrome- labelled antisera and the RBCs are passed through the laser beam of a flow cytometer. Flow cytometry
is reported to be equally or more sensitive than the Coombs test, but the Coombs test is considered to be more specific than flow cytometry.
Some in-house rapid diagnostic tests have also been developed that provide a yes/no answer (i.e. is the
dog Coombs positive?) within 30 minutes. Currently, in Europe the most widely available of these tests is that marketed by Alvedia (LabTest DAT). Not all of these tests have been validated against the gold standard full test (as described above), but those that have often show good correlation.
Further Reading
Caviezel LL, Raj K, Giger U. Comparison of 4 direct Coombs test methods with polyclonal antiglobulins in anemic and nonanemic dogs for in-clinic or laboratory use. J Vet Intern Med. 2014. 28: 583-591.
Day MJ. Arthropod-borne infectious diseases of the dog and cat. 2nd Edit. Taylor and Francis, London, 2016.
Day MJ, Kohn B (Editors). Manual of Canine and Feline Haematology and Transfusion Medicine. 2nd Edit. BSAVA, Gloucester, 2012.
Day MJ. Clinical Immunology of the Dog and Cat. 2nd Edit. Manson Publishing Ltd., London, 2012.
Day MJ, Schultz RD. Veterinary Immunology: Principles and Practice. 2nd Edit. Manson Publishing Ltd., London, 2014.
Harkin KR, Hicks JA, Wilkerson MJ. Erythrocyte-bound immunoglobulin isotypes in dogs with immune-mediated hemolytic anemia: 54 cases (2001-2010). J Am Vet Med Assoc. 2012. 241: 227.
Morley P, Mathes M, Guth A et al. Anti-erythrocyte antibodies and disease associations in anemic and non-anemic dogs. J Vet Intern Med. 2008. 22: 886- 892.
Piek CJ, Teske E, van Leeuwen MW et al. Good agreement of conventional and gel-based direct agglutination test in immune-mediated haemolytic anaemia. Acta Vet Scand. 2012. 54: 10.
Warman SM, Murray JK, Ridyard A et al. Pattern of Coombs test reactivity has di- agnostic significance in dogs with immune-mediated haemolytic anaemia. J Small Anim Pract. 2008. 49: 525-530.
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