Archive for February, 2014

“Dallas Buyers Club” and HIV testing

Monday, February 3rd, 2014

What would you do if you were tested positive for HIV in a routine blood exam? Well, this question came up after I saw the movie Dallas Buyers Club. The movie portrays the life of Ron Woodroof, who was a Texas cowboy and drug user and was diagnosed with AIDS in the 1980s. He was initially given 30 days to live, but Woodroof (portrayed by actor Matthew McConaughey) begins taking azidothymidine (AZT), the only HIV drug legally available in America at that time. Woodroof goes on to travel the world, searching for medications that will keep him alive, and as a result, the Dallas Buyers Club is formed.  With the help of a doctor and another patient played by Jared Leto as a transsexual, Woodroof begins selling smuggled drugs out of a motel in Dallas, providing HIV-positive patients with alternative forms of treatment for their disease, since the FDA was still testing the drugs that are currently used. Interestingly, the storyline closely reflects the real life events of Ron Woodroof and provides a great example of how patient advocacy hastened the development of effective HIV medications during the 80s. I watched the movie and it was clear how the process of drug approval and lab testing is still rudimentary. Coming back to my question in the beginning of this blog post, what if your HIV test comes back positive? Well, what if I say that the standard tests done for HIV have problems with numerous false-positives? The main and most widely test used is an immunoassay called ELISA that measures antibodies against the virus. However, viruses are very similar and have building blocks or proteins that look alike. So, when you measure antibodies against a response of the human body for a viral infection, false-positives can occur. Indeed, I am writing this post to give people awareness that, for example, flu vaccination could cause a false positive for HIV. Like I said, the viruses are very similar. The HIV GP160 protein exists in several viruses and has a lot of similar regions (see more at this report on the New England Journal of Medicine “Influenza Vaccination and False Positive HIV Results”). This protein is present in other virions too, especially a variety of flu related viruses. Thus, vaccination against any type of flu could generate a cross-reaction in the aforementioned immunoassay. In fact, there are several reports and groups of discussion online in which the most discussed subject is a false positive test result for HIV. Yes, that is scary and weird, but it is more common that we imagine. Given the escalating international awareness of various influenza strains and flu vaccination, it is very important for clinicians and patients to keep in mind that influenza vaccination may cause cross-reactivity with HIV antibody assays. The time course for such cross-reactivity remains mostly uncertain, but could be for months. If your HIV test was positive, take into account this possibility and ask for the use of a nucleic acid amplification test instead of the “Western blot” assay to confirm the enzyme immunoassay. People should and need to be aware of that. The movie Dallas Buyers Club just reminded me how science and research can be misleading within its own “rules”. Ron Woodroof tried to overcome these rules to save lives and himself. We all need to take care of ourselves, of course, using the law to do it. The take home message is that we still do not understand enough about the biology of viruses and confusions such as the one I discuss here could happen. So be aware!