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Mar 22, 2013

Hello, I just recently took an HIV test. I believe they took the western blot test. Every thing came back negative in it but P55 came back equivocal. I'm a nervous wreck so my question to you is what does that mean and what is P55?

Response from Dr. Hightow-Weidman

Hello there- While you mention your western blot results you do not state whether an ELISA was done first that was reactive. Standard HIV-screening blood test consists of an EIA (enzyme immunoassay), like an ELISA, followed by a confirmatory Western Blot (WB). EIA screening requires a "repeatedly reactive" test, which is the criterion for Western Blot testing. Western Blot tests detect antibodies to HIV-1 proteins, including core proteins (p17, p24, p55), polymerase proteins (p31, p51, p66) and envelope glyco-proteins (gp41, gp120, gp160). Western Blot testing should always be coupled with EIA screening, because alone it has a 2% rate of false-positives. A positive WB is defined as reactivity at gp120/160 plus either gp41 or p24. An indeterminate Western Blot is defined as the presence of any band pattern that does not meet the criteria for a positive result.

Bottom line: you are HIV negative.

If you recently had a high risk exposure I would recommend retesting in 3 months to ensure you remain negative. Take care, LHW

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