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How Accurate Are Blood Tests for Herpes?

According to the University of Maryland Medical Center, nearly every person in the United States – about 85% of the population – will be infected with herpes by the time they reach their sixties. If you’ve ever had one of those annoying cold sores on your tongue, you’ve already experienced an HSV outbreak. For most people, the herpes simplex virus will never present any lasting or major symptoms – but for people who become infected with genital herpes, a common STI which causes painful sores and flu-like symptoms, the virus is a serious medical issue which needs to be managed with antiviral medication. Of course, in order for herpes to be managed effectively, it needs to be diagnosed first – but just how accurate are our current testing methods? In this article, our Baltimore clinical malpractice attorneys will explain how herpes is diagnosed, which tests are most accurate, and what to do if you or your partner was the victim of a herpes misdiagnosis.

How Do Doctors Test for Genital Herpes?

There are two types of herpes simplex virus: HSV-1, which causes cold sores (oral herpes/herpes simplex labialis), and HSV-2, a similar virus which the World Health Organization says is responsible for the majority of genital herpes cases in the U.S. Genital herpes is usually caused by HSV-2 transmission by skin-to-skin contact during intercourse, but can also be transmitted by genital-to-mouth contact with the HSV-1 virus (cold sores around the lips/tongue).

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Regardless of whether genital herpes is initially caused by HSV-1 or HSV-2, the end result is the same: recurring flare-ups whose effects can include fever, swollen lymph nodes, painful urination, and stinging, running, itchy blisters, which usually start to scab and heal over within several weeks.

Because these symptoms can lie dormant for long periods of time, and because the virus can easily spread in a variety of ways, herpes is highly transmissible and should be tested for promptly if you have any suspicions of an infection. There are a few different types of tests your doctor can perform to diagnose genital herpes, including:

  • Antibody Tests (IgM, IgG) – The body naturally responds to an HSV infection by creating two types of antibodies (blood proteins whose function is to fight off viruses and bacteria): IgM, and IgG. IgG becomes detectable shortly after the infection develops, and stays in the person’s body for the rest of their life. IgM is detectable almost immediately, but unlike IgG, can disappear later on. Your doctor will take a blood sample, which will be tested for IgG or IgM antibodies at a medical lab.
  • Cell Culture – Your doctor will take a swab from a sore to examine under a microscope. If you don’t have any symptoms, you might need to take a blood test instead.
  • PCR Blood Tests – A PCR blood test can detect herpes even if you don’t have any physical symptoms. Your doctor will take a blood sample, which will be lab-tested to see whether any evidence of the virus’ DNA is present.

How Often is Herpes Misdiagnosed, and Which Tests Are the Most Accurate?

While it would be a stretch to deride any herpes tests as useless, some diagnosis methods consistently produce higher accuracy rates than others.

According to the American Sexual Health Association (ASHA), an award-winning non-profit organization founded more than 100 years ago, PCR blood testing is one of the “preferred methods” of herpes testing. ASHA describes PCR blood tests, which are a type of Nucleic Acid Amplification Testing (NAAT), as “fast” and “accurate,” adding that “there is less chance of a false negative result with NAATs.” Today, PCR blood testing is the most common NAAT testing method.

ASHA’s assessment of antibody tests – at least, IgM antibody tests – is less enthusiastic. In fact, ASHA explicitly recommends against using IgM tests, for three important reasons:

  1. IgM tests can accidentally pick up on other viruses, including cytomegalovirus (CMV) and varicella zoster virus (VZV), which can lead to confusing diagnoses of mono or chickenpox.
  2. IgM has the potential to disappear and reappear in the body, and to make matters more confusing, these patterns aren’t consistent, as IgM only reappears in about one third of infected patients.
  3. Unlike PCR blood tests, IgM tests aren’t sensitive enough to distinguish between HSV-1 and HSV-2. Because nearly everyone carries HSV-1, a healthy person could receive a false positive that says they have HSV-2 when they actually don’t. That could lead the person to take medications they don’t actually need (and to spend money they don’t need to spend).

While ASHA is critical of IgM antibody tests, IgG antibody tests score high marks for accuracy. According to ASHA, “100% of the labs using [I]gG-based tests accurately reported that the blood sample was negative for HSV-2,” compared to as many as 88% of IgM tests coming back with false positives (mistaking HSV-1 for HSV-2). However, there’s still a problem: IgG levels are detectable in some people after weeks, while others take months to reach the same point. In light of these inconsistencies, it’s a good idea for patients to undergo multiple test sessions to confirm initial results.

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While some herpes tests have high accuracy rates, misdiagnosis is always a risk – especially because, as a recent study in Current Infectious Disease Reports points out, “Even experienced clinicians can misdiagnose ‘atypical’… vesicles and ulcers.” Atypical herpes symptoms can include:

  • Fissures
  • Lesions which appear on the thighs, groin area, or buttocks
  • Vulvar erythema (in women)

If you or your boyfriend, girlfriend, or spouse suffered injury because of a herpes misdiagnosis, you may be able to recover compensation to help with your medical bills and expenses. Call the lab test error attorneys of Whitney, LLP at (410) 583-8000 to set up a free and private consultation today.

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