Lyme Disease vs HIV testing
Dec 8, 2005
Hi Can you please explain the similarities and differences between lyme disease testing and hiv testing? Is it possible for someone who has been tested positive for the ELISA and western blot tests may not neccessarily be infected with HIV? The reason I'm asking because my girlfriend tested positive for HIV twice within the last six months but i've been tested twice over a year and i'm negative. My most recent test was done in November. We had unprotected sex over the past 2 years. I truly believe she was faithful to me and hence find it very hard to accept the test results. I also read that the ELISA and WB tests do not detect the HIV virus strain itself but the antibodies present when the virus exists. I read also that there are over 70 different conditions where these antibodies can be present and are not caused by the HIV strains. What are the conditions for ELISA and WB false positives and what further tests can be done to get a conclusive result for HIV.
Response from Dr. Wohl
The combination of ELISA and Western blot are very good at detecting HIV. The ELISA is less specific but is sensitive - menaing it has permits false positives so as not to miss people with antibodies to HIV. The Western blot is more specific so that a positive result almost always means that HIV antibodies were detected.
No test is perfect but this is close. However, in conditions where there are lots of antibodies are produced such as pregnancy or autoimmune diseases, these antibodies can trip up the ELISA and even the Western blot and lead to false positive tests. That is still pretty unusual.
The HIV viral load can detect the actual virus rather than the antibodies it provokes. IF your girlfriend has detectable HIV by the HIV RNA PCR (viral load) test, there is no doubt that she is HIV infected.
That you are not HIV+ does not mean she is not. Such discordance betwen couples is well described. Most evidence suggests that over time there is a steady rate of conversion from HIV negative to positive among the initally uninfected partner.
Not all infections can be diagnosed equally well with antibody tests. Different infections produce different types and levels of antibodies that may not all be as readily detected by ELISA or Western blot tests.
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