Felis ISSN 2398-2950

Direct Coombs' test

Synonym(s): Direct antiglobulin test

Contributor(s): Karen Gerber, Michael Day

Overview

Sampling

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Tests

Methodologies

  • Patients red cells are washed then mixed with antiserum containing antibodies against feline immunoglobulins (IgG, IgM) and complement (polyvalent feline Coombs' reagent) and titrated to dilutions of at least 1 in 10,000.
  • Also titrate individual antisera against feline IgG, IgM.
  • Incubate at 37°C for 1 hour. Ideally test performed in duplicate also at 4°C.
  • Observe for agglutination. (Small red flecks of agglutinated cells are seen suspended in the solution in the well. If there is no agglutination, a large red dot is seen in the bottom of the well.)

Availability

  • Most commercial veterinary laboratories (but generally only polyvalent reagent is used at 37°C with limited titration).

Validity

Sensitivity

Specificity

Technique (intrinsic) limitations

Technician (extrinsic) limitations

False negatives may result from incorrect laboratory procedures

  • Reagents not specific to feline immunoglobulins.
  • Test performed at incorrect temperature.
  • Prozone phenomenon: if the anti-immunglobulins used in the test bind the antibody-coated cells too avidly, then agglutination may be prevented. Overcome by routinely performing test at serum dilutions up to 1:10,000.

Result Data

This article is available in full to registered subscribers

Sign up now to purchase a 30 day trial, or Login

Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Stokal T & Blue J T (1999) Pure red cell aplasia in cats: 9 cases (1989-1997). JAVMA 214, 75-79.
  • Gunn-Moore D, Day M J, Graham M E A, Cue S M & Harbour D A (1999) Immune-mediated haemolytic anaemia in two sibling cats associated with multicentric lymphoblastic infiltration. JFMS 1, 209-214.
  • Person J M et al(1997) Les anemies hemolytiques auto-immunes dans le chat. Revue Med Vet 148(2), 107-114.
  • Eibert M & Lewis D C (1997) Evaluation of the feline erythron in health and disease. Comp Cont Educ Pract Vet 19335-347.
  • Day M J (1996) Diagnostic assessment of the feline immune system. Part 2. Feline Practice 24, 14-25.

Other sources of information

  • Day M J (1999) Clinical Immunology of the dog and cat. London: Manson Publishing. ISBN: 1 8745 4598 7.


ADDED