Felis ISSN 2398-2950

FIV test

Contributor(s): David Godfrey

Overview

  • Feline immunodeficiency virus (FIV) Feline immunodeficiency virus contains gag proteins (eg p24 or gp40).
  • Antibodies to these proteins can be detected by screening tests, usually enzyme linked immunosorbent assay (ELISA) Enzyme linked immunosorbent assay (ELISA), concentration immunoassay, (CITE) and rapid immunomigratory (RIM) tests.
  • Western blot tests and immunofluorescent antibody test (IFA) Indirect immunofluorescence can confirm screening test results.
  • Polymerase chain reaction (PCR) assays detect proviral DNA. These are somewhat specific to the particular FIV subtype and are most reliable in relation to subtype A. FIV subtype A is currently the only type found in the UK. Types A and B are found in continental Europe and types A, B and C in North America.
  • Testing is critical to diagnosis and control of FIV disease Feline immunodeficiency virus disease.

Sampling

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Tests

Methodologies

  • ELISA Enzyme linked immunosorbent assay (ELISA), CITE and RIM - commercially available kits for use in practice laboratory as a screening test. Some are found in combination with a FeLV antigen test.
  • Western blot - confirmatory test.
  • IFA serology.
  • PCR for FIV provirus DNA.

Validity

Sensitivity

  • Most available screening tests have a sensitivity in range 86 - 97%. False negatives are due to inadequate time for seroconversion, large viral load binding to all available antibody or immunodeficiency and diminished production of antibody during immunodeficiency.

Specificity

  • There is high specificity but this does not necessarily denote a good positive predictive value. False positives are seen due to parallel positive reactions between test reagents and other factors (non-FIV-related) in the sample.

Predictive value

  • The predictive value of testing depends on the population being tested. False positive antibody screening tests occur (ELISA, CITE or RIM tests). These are particularly relevant when testing healthy animals or animals from a group unlikely to be FIV infected. In these situations then it may be that most positive tests are actually false positives and a minority are true positives. However, if testing a cat from a higher risk situation, eg one with signs of FIV-associated disease or with a known history of aggressive fighting a positive result on a screening test is likely to be a true positive (it should still be confirmed using a different methodology).
  • Presence of antibodies to FIV is strongly correlated with persistent infection, but is not diagnostic for clinical disease. Many FIV positive cats are not ill, many that are ill have another primary problem and the FIV infection has been found coincidentally.
    When interpreting result take into account likelihood of cat having disease.All positive results from a screening test (ELISA, CITE or RIM) and any unexpected negative result should be followed up using a confirmatory test - IFA, PCR (in the UK) or Western Blot.

Result Data

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Hosie M J, Addie D, Belak S et al (2009) Feline immunodeficiency. ABCD guidelines on prevention and management. J Feline Med Surg 11, 575-584 PubMed.
  • Hartmann K, Greissmayr P, Schulz B et al (2007) Quality of different in-clinic test systems for feline immunodeficiency virus and feline leukaemia virus infection. J Feline Med Surg 9, 439-445 PubMed.
  • Hartmann K, Werner R M, Egberink H, Jarrett O (2001) Comparison of 6 in-house tests for the rapid diagnosis of feline immunodeficiency and feline leukaemia virus infections. Vet Rec 149, 317-320.
  • Hosie M J et al (1998) DNA vaccination affords significant protection against feline immunodeficiency virus infection without inducing detectable antiviral antibodies. J Virol 72(9), 7310-7319.
  • Robinson A et al (1998) Comparison of a rapid immunomigration test and ELISA for FIV antibody and FeLV antigen testing in cats. Vet Rec 142(18), 491-492.
  • Troy G C et al (1996) Proficiency testing of selected antigen and antibody tests for use in dogs and cats. JAVMA 209(5), 914-917.
  • Barr M C (1996) FIV, FeLV and FIPV: interpretation and misinterpretation of serological test results. Semin Vet Med Surg (Small Anim) 11(3), 144-153.
  • Sibille P et al (1995) Comparison of serological tests for the diagnosis of feline immunodeficiency virus infection of cats. Vet Microbiol 45(2-3), 259-267.


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