Oral STDs: Pictures, types, symptoms, treatment, and prevention
False Positive Results On HIV Tests
Key pointsThe ideal HIV screening test would correctly identify all HIV-positive and HIV-negative individuals 100% of the time. While many HIV tests are extremely accurate, they do not achieve 100% accuracy.
A false positive is a test result that says a person has HIV when, in fact, they do not have it. Because it is upsetting and disturbing to receive a false positive result, preliminary positive ('reactive') results must always be verified with a series of confirmatory tests.
What causes false positive results?HIV tests are based on the detection of antibodies to HIV. These are proteins produced by the immune system in response to a foreign substance, such as HIV. The main cause of false positive results is that the test has detected antibodies, but they are not antibodies to HIV – they are antibodies to another substance or infection. Tests are not meant to react to other types of antibodies, but it sometimes happens.
There are other reasons why a test may give a false positive result. Depending on the testing device, reading the test result may rely on subjective interpretation. When the result is borderline, experienced staff give more consistently accurate results. A false positive result could also be the result of a sample being mislabelled, mixed up with another person's, or some other clerical or technical error.
Less commonly, false positive results may occur in people who have recently had a flu vaccine, are taking part in an HIV vaccine study, or have an autoimmune disease (such as lupus).
Reactive results and follow-up testingBecause of the possibility that a positive result from a single test is, in fact, a false positive, most healthcare professionals prefer to talk about the result being 'reactive' rather than 'positive'. If the result is reactive, this indicates that the test has reacted to something in your blood and needs to be investigated further.
This preliminary result must be verified with a series of confirmatory tests. If the initial test was done on a rapid, point-of-care test, you might do a follow-up test with a second rapid test that works in a slightly different way. If you provided a blood sample for analysis in a laboratory, the staff there will run several tests on the sample before telling you the result.
My test result is reactive. What's the chance that this is a false positive?If you tested in a healthcare facility, the staff there should make sure you have the necessary follow-up tests. This sequence of confirmatory tests is carefully planned to prevent inaccurate results from being given. Healthcare professionals call it a testing algorithm. If you have been tested in this way, with a sequence of confirmatory tests, and you have been told that you are HIV positive, you can be confident of the result. The rest of the information on this page does not apply to you.
On the other hand, you might have been tested with a rapid, point-of-care test at a location where the staff could not do the confirmatory tests immediately. If your initial result was reactive, the staff may have asked you to come back on another day or to go to another healthcare facility for the follow-up testing. Or you might have taken the test yourself, using a device for self-testing or home testing.
"An HIV diagnosis is never made on the basis of a single test result."
If that is the case, the confirmatory testing is essential. There is a possibility that your reactive result is in fact a false positive. The only way to know is to go and have it checked by a qualified healthcare professional.
The accuracy of a single HIV test depends in part on characteristics known as sensitivity and specificity. Sensitivity is an indication of test performance when testing people who do have HIV, whereas specificity reflects test performance in relation to people who do not have HIV. Many modern HIV testing devices are extremely sensitive (over 99%) and extremely specific (over 99%). There's more information on sensitivity and specificity on another page.
The chances of having a false positive also depend on how common HIV is in your community. False positive results are quite a rare event, but in a community where very few people have HIV, true positive results are even rarer. In a setting where HIV is more common, a reactive result is less likely to be a false positive.
Glossary reactiveBecause of the possibility that a positive result from a single HIV test is, in fact, a false positive, the result is described as 'reactive' rather than 'positive'. If the result is reactive, this indicates that the test has reacted to something in the blood and needs to be investigated with follow-up tests.
false positiveWhen a person does not have a medical condition but is diagnosed as having it.
specificityWhen using a diagnostic test, the probability that a person without a medical condition will receive the correct test result (i.E. Negative).
sensitivityWhen using a diagnostic test, the probability that a person who does have a medical condition will receive the correct test result (i.E. Positive).
antibodyA protein substance (immunoglobulin) produced by the immune system in response to a foreign organism. Many diagnostic tests for HIV detect the presence of antibodies to HIV in blood.
For example, take a test with 99.5% sensitivity and 99.5% specificity. If this test is used in a setting where 0.2% of people have HIV (for example, among the general population in the UK), the probability of a reactive result being correct is 28.5%. The number of people given an incorrect reactive result (71.5%) is greater than the number given a correct result (28.5%).
In contrast, if the same test is used in a setting where 8% of people have HIV (for example, among gay and bisexual men in the UK), the probability of a reactive result being correct is 94.5%. There are far fewer false positives (5.5%), but they still occur.
The figures describing the probability of a reactive result being 'true' are known to healthcare workers as the 'positive predictive value'. Some more examples, all based on a test with 99.5% sensitivity and 99.5% specificity, are given below.
Prevalence of HIV
Examples of settings with this prevalence of HIV
Probability that a reactive test result reflects a true HIV infection (positive predictive value)
0.1%
General population in Australia
16.6%
0.2%
General population in the UK, Sweden or India
28.5%
1.4%
African Americans in the US
73.8%
5%
General population in Kenya; female sex workers in Brazil
91.2%
8%
Men who have sex with men (MSM) in the UK
94.5%
18%
General population in South Africa; MSM in Malawi
97.7%
30%
General population in KwaZulu-Natal, South Africa; MSM in Bangkok, Thailand; female sex workers in Kenya
98.8%
To put this in individual terms:
For these reasons, an HIV diagnosis is never made on the basis of a single test result. All reactive (potentially positive) results are checked with extra confirmatory tests.
The positive predictive value of a testing algorithm, using a sequence of two or three different tests, is almost 100%. If a positive result has been confirmed in this way, you can be confident that it is accurate.
Find out more about the accuracy of HIV testingFor more information about HIV test accuracy, read our pages on sensitivity and specificity and on window periods. Our research briefings contain detailed information about the accuracy of fourth-generation combination tests, rapid point-of-care tests and self tests.
Where You Live Is As Important As What You Eat
It's what people eat, what they breathe, how they move. The built environment, of which transport infrastructure is part. This includes how easy it is to walk or cycle. And by easy, I mean access, but also how easy it is to do that without risking life and limb.
It's also access to green space, which influences mental health and physical health in terms of space needed to be physically active, but it's also infrastructure that reduces exposure to extreme heat. And also our student environment, our levels of air pollution, the risk of injury.
These are the factors that determine our health.
Haze shrouds the skyline of Brooklyn and buildings in Manhattan as seen from the Empire State Building.Photograph: Gary Hershorn/Getty Images
A monorail train is seen passing through cityscape engulfed in smog (mixture of smoke gases and chemicals in the air) in Mumbai.Photograph: Ashish Vaishnav/Getty Images
In this aerial view, smoke haze from fires blankets the city of Santa Cruz, Bolivia, on October 25, 2023.Photograph: RODRIGO URZAGASTI/Getty Images
The city skyline is pictured amid high levels of air pollution in Bangkok on October 18, 2023.Photograph: ALEX OGLE/Getty Images
Are there some cities that, broadly speaking, are "healthy"? Who sets a good example?
It's a difficult question. Averages hide a lot. I'm always loath to say one city has others beaten.
The easiest thing to say is that maybe in places where inequality is lower, where healthy public space is much more fairly and equitably distributed, things are better.
London is a fairly good city to be physically active and to be outdoors—lots of green space—but it's highly inequitable in terms of who has access to that. And it's highly inequitable in terms of the quality of air that people breathe. Even in cycling infrastructure. There are some parts of London that you have to be very risk-embracing to be a cyclist.
So the big question: How do you make a city healthier?
A lot of the work I do is on identifying risks—better connecting health and climate risks to what may seem like a good thing.
For example, if you have new road infrastructure coming into cities and then growing rapidly, that's generally a mark of development—helping people become more mobile and facilitating economic activity.
But where there weren't big roads before, now you have big roads where cars can move very quickly. As the speed of cars increases, so does the risk of injury. Maybe people need to get from this side of the road to that side. Or it's displacing cycling infrastructure.
Often with developers of public spaces it's a sin of omission rather than of commission. It's just, "We will just cut and paste and do things this way, because we've got a template." Nobody's asking for clean air, and nobody's asking for walkability. What is rarely apparent is what the health cost is, because that cost is born in a different sector and often at a different time.
Tattoos: A Journey Of HIV Acceptance
Tattoos make him feel freeSTORY HIGHLIGHTSPortland, Oregon (CNN) -- As he puts a straw in his fruit smoothie, Michael Lee Howard accidentally knocks over the cup, spilling the seaweed-colored liquid. "Well, it happens," he says. As he collects the smoothie overflow in the plastic lid, he exposes the tattoos on his wrists: a biohazard symbol on the right and a radiation symbol on the left.
Howard might not have come across as such a calm person in late 2005, when he found out he was HIV-positive. After his diagnosis, he felt "dirty" in his own skin, and feared infecting others if he so much as cut his hand. Getting the wrist tattoos helped him in his journey toward self-acceptance.
"It's a branding of who I am, and it's a branding of being comfortable with that, being comfortable with who I am," said Howard, 37, who lives in Portland, Oregon.
Howard is one of many people living with HIV who have chosen to get tattoos to represent living with the disease. They say these tattoos help start conversations, reduce stigma and serve as reminders of how living with HIV has changed their lives.
Tattoos like Howard's biohazard symbol are especially common in men who have sex with men, the subpopulation that bears the highest burden of new HIV infections in the United States. Men who have sex with men accounted for 61%, or 29,300, new HIV infections in 2009, federal health officials said last week. And although the number of new HIV cases has remained stable in the general population, new infections rose among young, black gay and bisexual men from 2006 to 2009.
It was also among men having sex with men that U.S. Doctors first realized, in 1981, that there was a never-before-seen disease that could destroy the immune system. That disease came to be known as human immunodeficiency virus.
"In the gay male community, we think about it (HIV) a lot more because it attacked our community first. It's wiped out a number of us," said William Conley of Pollock Pines, California. His tattoo, a biohazard symbol with the Celtic motif of a crown of thorns circling around it, means he's winning the fight against this disease.
"You're not a victim. You're a champion, you are a survivor, and that's the biggest part of the tattoo," Conley said.
Identification and awareness
The origins of HIV-related tattoos are murky, but the biohazard symbol is recognized in connection with HIV among many gay men, said David Dempsey, clinical director at the Alexian Brothers Bonaventure House in Chicago and The Harbor in Waukegan, Illinois, both transitional living facilities for HIV-positive individuals recovering from alcohol and substance dependence.
"It's to let other men know that they're HIV-positive so that they don't have to come out and say it," he said. In situations of anonymous sex, it can signal status to potential partners and, in that sense, may help with prevention, because unprotected sex with an HIV-infected individual can spread the disease, he said.
For those with HIV, seeing someone else with a biohazard symbol is a sign this is another person living with the disease who might provide support, Conley said, like a "secret identification code."
There are less cryptic HIV tattoos, too. Dempsey has a red AIDS ribbon tattoo on his chest, which he chose even before he became HIV-positive (the organization Visual AIDS created the ribbon symbol in 1991). Dempsey has been a social worker in the HIV community for 11 years, and wanted to show solidarity with people living with the disease, as well as raise awareness.
In 1986, when AIDS was just starting to be recognized as a deadly illness transmitted through sex and intravenous drug use, conservative author William F. Buckley Jr. Suggested HIV-positive people get tattoos to protect others. He wrote in The New York Times, "Everyone detected with AIDS should be tattooed in the upper forearm, to protect common-needle users, and on the buttocks, to prevent the victimization of other homosexuals."
Some HIV-positive individuals may have gotten tattoos in resistance to Buckley's article, said Richard Sawdon Smith, professor of photography and AIDS cultures at London South Bank University in the United Kingdom, who has been HIV-positive since 1994. This is not an oft-cited reason among people with tattoos today, although many of the people who got HIV in the '80s and may have gotten tattoos then have since died.
Another theory is that certain ACT UP activists sported biohazard tattoos in their massive demonstrations in the late '80s and early '90s, but founder Larry Kramer said he hasn't heard of these tattoos or of the organization's participation in the practice.
Tattooing HIV-related symbols has been going on at least since Nick Colella started at Chicago Tattooing and Piercing Company in 1994.
Colella used to tattoo more memorial motifs honoring people who had died of AIDS when he was starting out -- less so now, since modern antiretroviral medications effectively let patients live long lives with HIV as a chronic illness. Colella, like other tattoo artists, sterilizes his equipment and throws used needles away in biohazard-labeled containers so diseases transmitted through blood, including HIV, do not spread from person to person.
Showing the world his HIV-positive status through tattoos was like a second coming out for Michael Lee Howard. Biohazard symbols and ribbons are just some of the representations of HIV-positive status that Colella has tattooed, he said. He sees this business pick up annually during Chicago Pride Fest.
"People symbolize happiness, sadness, sexuality, everything with tattoos. It's all the good, all the bad, all the everything," he said.
Some people get HIV-related tattoos immediately after getting a positive test result. Conley waited three days after his diagnosis in 2009 to get his tattoo.
Conley, a sociologist by training, knows of 45 to 60 others in online forums who have tattoos involving a biohazard symbol or a scorpion, another sign of having HIV in the gay community. The stinging tail of the scorpion alludes to the virus, he said.
"Basically saying, 'I'm positive and you need to know that, especially if we're going to engage in any intimate relation' -- it has that meaning," he said.
Coming to terms with diagnosis
Howard found out about the biohazard sign as a symbol for the HIV-positive gay community through the Internet. The radiation design, though, was his own idea. He chose it because in comic books, when superheroes get radiated, life "starts from scratch," he said.
That's what Howard felt like he needed: A rebirth. Getting HIV had been a total shock. He had briefly dated a man who said he didn't have sexually transmitted diseases, but later Howard found out the man was HIV-positive and had given him the virus. Before then, Howard didn't know anyone who was HIV-positive.
His diagnosis was a wake-up call to better his life. Deep down, he said, he wasn't a happy person and wasn't being his true self on his blog, which felt like "a Hello Kitty commercial" -- too perky for what he actually felt. He went into three years of intense therapy in an effort to find his "authentic self."
"I just got tired of being what everybody else wanted me to be," he said. "I think that's part of where the tattoos came in: I didn't get tattoos or as many piercings, because that's not what you do. You do what everyone tells you to do."
"After my diagnosis I'm like, 'Well hey, I have nothing left to lose.' "
Showing the world his status through the tattoos was like a second coming out for Howard. And the responses from others about the tattoos have been overwhelmingly positive. Since his tattoos are so prominent, Howard gets asked about them all the time. They give Howard opportunities for dialogue about living with HIV, with everyone from fellow light-rail commuters to his boss.
Talking about it
Opening up those kinds of conversations is why Chad Hendry, 32, got a bold tattoo from Colella in July. On his neck is a red AIDS ribbon with the words "On this day my new life began" and the date of his diagnosis: 12-30-09.
He's not sure whether he got HIV through sex or drugs; he knew his behavior was risky, but he never thought he'd get the disease. After about a year, though, his health declined, and a test showed he had HIV. Rehab helped him curb his crystal meth addiction, and his grandparents helped him get back on his feet. He lives in an HIV recovery home near Chicago.
A red HIV T-shirt campaign gave him the idea that he wanted a tattoo related to his status. People would see the shirt and ask questions about living with the virus; with a tattoo, Hendry could have that level of engagement all the time.
"It's the same reason I'm very vocal about it: because I believe that will make the path just a little bit easier for somebody else," he said.
But the tattoo hasn't entirely brought him comfort. Hendry fears he might not find a partner who is comfortable with the statement of the tattoo. His family members weren't entirely welcoming of it -- they wondered why it had to be so prominent on his neck. People on trains seem to stare at it, too.
Still, Hendry loves his tattoo. He's not ashamed of having HIV; in fact, he feels it's one of the best things that has happened to him, because he's off drugs and has a better outlook on life.
"Today I live every day with gratitude. You become grateful for what you have in being alive," he said.
The ribbon motif also appealed to Howard of Portland. To commemorate his five-year "posiversary" in November, he got a red ribbon tattoo on his shoulder with his diagnosis date.
"I think that I'm the most comfortable and happy in my own skin that I've ever been in my entire life," Howard said.
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