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HIV Western BlotAka: HIV Confirmatory Test

Indication
1. Used to confirm positive HIV EIA (HIV Screening Test)
Mechanism
1. Direct visualization of antibodies to HIV components
  1. Components: Env, Gag, Pol
  2. Antibodies: p24, gp41, gp120, gp160
  3. Band forms if Antibody present to that component
2. Positive Test
  1. Two or more bands from p24, gp41, gp120 or qp160
Efficacy
1. Reliably identifies HIV-1
2. False negative causes
  1. Group O protein (10% false negative rate)
  2. HIV-2 (20% false negative rate)
  3. Early seroconversion (less sensitive than HIV ELISA)
3. False positive causes
  1. Hyperbilirubinemia
  2. Connective tissue disorder
  3. Polyclonal Gammopathy
Follow-Up evaluation for indeterminate or negative test
1. Repeat Western blot in 1-3 months
2. Consider Western blot for HIV-2
References
1. Demeter in Mandell (2000) Infectious Disease, p. 1371

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This page was written by Scott Moses, MD. This page was last revised before 5/10/08, prior to consistent tracking of revision date. This page was last published on 6/1/2008. Please send comments and questions to the editor. Contact information may be found on the page About the Family Practice Notebook. These pages are best viewed with Microsoft Internet Explorer 6.0.