Can a yeast infection cause a false positive herpes test

No one wants to discover they have herpes, especially genital herpes. And believe it or not, many people never do: An astonishing 80% of people with herpes simplex virus (refresher: HSV-1 usually causes oral herpes, while HSV-2 is usually to blame for the genital kind) never have any symptoms. The remaining 20% of cases that do bring symptoms can be—and often are—mistaken for other things.

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“There are lots of asymptomatic infections and the occasional person who has a really horrible outbreak,” says Jeanne Marrazzo, MD, member of the board of the Infectious Diseases Society of America and director of the Division of Infectious Diseases at the University of Alabama at Birmingham.

Of course, you’ll want to take the necessary steps to prevent herpes, regardless of whether or not you’re infected. Condoms can reduce the risk of herpes transmission, especially for men. “In men, condoms cover the relevant portion,” says Dr. Marrazzo. “For women, it’s harder to cover everything, so condoms reduce the risk by one-third to one-half.” If you know you have herpes, you can also take medications that reduce the risk of transmission.

If you think you could have genital herpes, here’s what else might be to blame.

Yeast infections

Some 75% of women will be diagnosed with a yeast infection in their lifetime, and it may be mistaken for herpes. “For women, the most common confusion is recurrent yeast infections, particularly when they infect the outer labia,” says Dr. Marrazzo. Most of the time, though, a yeast infection is just a yeast infection—and one that can be treated easily with over-the-counter meds.

If you already know you’re prone to yeast infections, “that’s probably what it is,” Dr. Marrazzo says. Warning signs that something else might be up down there include anything out of the ordinary for you, particularly “a recurrent pattern, for example every three to six months, or around stress. That’s a little bit unusual for a yeast infection,” she says. Symptoms that appear after having sex with a new partner may also signal herpes.

Bacterial vaginosis

Bacterial vaginosis is basically an imbalance of the normal bacteria universe in your vagina. It’s not considered a sexually transmitted infection (STI), but it is more common in sexually active women, and it can increase your risk of contracting an STI.

Douching, vaginal deodorants, and other vaginal products seem to up the risk of BV. Like herpes, BV often has no symptoms, but when it does, you might experience vaginal discharge, pain, itching or burning, and a fishy odor. The external skin itching and discomfort are what many people mistake for herpes. Bacterial vaginosis is treated with antibiotics.

Trichomoniasis

Trichomoniasis is a sexually transmitted infection, one caused by a small parasite. Like both herpes and bacterial vaginosis, the infection often has no symptoms. When it does have symptoms, they can also be mistaken for herpes: itching, burning, and redness in the genital area; difficulty urinating; and vaginal discharge. It’s easily treated with medication.

But don’t assume that a discharge in particular is a sign of an STI like trichomoniasis or herpes. “The reality is most people having an increase in discharge are just experiencing cyclic changes with hormones,” says Dr. Marrazzo. “What’s not normal is an abnormal odor. That goes with bacterial vaginosis or trichomoniasis.”

Syphilis

Once practically a death sentence, today the STI syphilis is easily cured with antibiotics like penicillin. Initial symptoms of syphilis (called primary syphilis) are one or more sores in or near the genitals, anus, or rectum that might be mistaken for herpes. Generally, the sores are round and firm, but they don’t hurt.

Once syphilis has progressed to the next stage (secondary syphilis), symptoms can include a skin rash as well as swollen lymph nodes and a fever as your body tries to fight the infection. Sometimes there are no symptoms in these first two phases, or the symptoms are tame enough to go unnoticed. It’s important to get syphilis treated as early as possible.

Urinary tract infection

A UTI is less commonly mistaken for herpes, but it can cause significant pain in the genital region. Other symptoms should tip you off that it’s a UTI and not herpes though: Look for an urgent feeling that you need to urinate; only passing a small amount of urine at a time (even though it may feel like your bladder is full); and urine that is cloudy, discolored, red, pink, or smelly. If your UTI doesn’t go away, get treatment. Untreated infections can affect your bladder and kidneys

There are different tests available for herpes. Viral culture and DNA tests can be done if you are experiencing symptoms. Blood tests are available for people who may not have had symptoms or if the signs have already healed.

Testing with symptoms

When a person has active herpes lesions (a.k.a. blisters, sores, ulcers), a swab can be taken and tests done that can detect the virus directly.

The tests used include culture and Nucleic Acid Amplification Testing (NAAT). Both culture and NAAT tests can identify the specific herpes virus type someone is infected with, but NAAT methods are more sensitive. Culture can easily miss infections and give false negative results.

Because a culture works by requiring virus that is active, if a lesion is very small, or is already beginning to heal, there may not be enough virus present for an accurate culture. Beyond 48 hours of the symptoms appearing, there is a risk of receiving a false negative test result. Viral culture is even less accurate during recurrences (positive in only about 30% of recurrent outbreaks).

NAAT methods are the preferred method, with PCR as the most-widely used NAAT method. These tests are fast, accurate, and can tell if a person has HSV-1 or HSV-2. There is also less chance of a false negative result with NAATs.

Testing with no symptoms

Blood tests can be used when a person has no visible symptoms but has concerns about having herpes. Blood tests do not actually detect the virus; instead, they look for antibodies (the body’s immune response) in the blood.

IgM vs. IgG

When an individual contracts herpes, the immune system responds by developing antibodies to fight the virus: IgG and IgM. Blood tests can look for and detect these antibodies—not the virus itself. IgG appears soon after infection and stays in the blood for life. IgM is actually the first antibody that appears after infection, but it may disappear thereafter.

IgM tests are not recommended because of three serious problems:

• Many assume that if a test discovers IgM, they have recently acquired herpes. However, research shows that IgM can reappear in blood tests in up to a third of people during recurrences, while it will be negative in up to half of persons who recently acquired herpes but have culture-document first episodes. Therefore, IgM tests can lead to deceptive test results, as well as false assumptions about how and when a person actually acquired HSV. For this reason, we do not recommend using blood tests as a way to determine how long a person has had herpes. Unfortunately, most people who are diagnosed will not be able to determine how long they have had the infection.
• In addition, IgM tests cannot accurately distinguish between HSV-1 and HSV-2 antibodies, and thus very easily provide a false positive result for HSV-2. This is important in that most of the adult population in the U.S. already has antibodies to HSV-1, the primary cause of oral herpes. A person who only has HSV-1 may receive a false positive for HSV-2.
• IgM tests sometimes cross-react with other viruses in the same family, such as varicella zoster virus (VZV) which causes chickenpox or cytomegalovirus (CMV) which causes mono, meaning that positive results may be misleading.

The accurate herpes blood tests detect IgG antibodies. Unlike IgM, IgG antibodies can be accurately broken down to either HSV-1 or HSV-2. The challenge here is that the time it takes for IgG antibodies to reach detectable levels can vary from person to person. For one person, it could take just a few weeks, while it could take a few months for another. So even with the accurate tests, a person could receive a false negative if the test is taken too soon after contracting the virus.

For the most accurate test result, it is recommended to wait 12 – 16 weeks from the last possible date of exposure before getting an accurate, type-specific blood test in order to allow enough time for antibodies to reach detectable levels.

There are currently several FDA-approved, gG-based blood tests that can give accurate results for herpes. Like any blood test, these tests cannot determine whether the site of infection is oral or genital. However, since most cases of genital herpes are caused by HSV-2, a positive result for type-2 antibodies most likely indicates genital herpes.

Herpes experts H. Hunter Handsfield, MD, and Kees Reitmeijer, MD, PhD, explain the types of herpes tests available, what tests are preferred for those with or without symptoms, and what test to avoid. See more of their conversation on sexualhealthTV.org. Have a question about herpes you’d like Dr. Handsfield or our other experts to answer? Visit Ask the Experts to learn how.

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