Medical questions & health advice by board certified doctors
"What is a false positive when it comes to a blood test?"
I was getting screened for STD's and HIV by my doctor, which I do every few months as a precaution. I asked her about a test for herpes, but she said they don't do blood tests because they can just be false positives. What does this mean? Would it tell me I have it even though I don't?
As you have noticed, the terminology for testing can be confusing, but you are correct that a false positive result means that the test diagnoses a positive result even thought the patient is negative. You should follow up with your primary care doctor to discuss this test in more detail. It is fairly well known that the Herpes testing currently available is not the most accurate to determine the STD strain of Herpes (Type 2 vs Type 1). Actually, many people have Type 1 Herpes which manifests as oral cold sores. The blood tests that are currently available for Herpes results with many positive findings. However, many of the patients for whom the test is positive do not actually have Herpes, thus, making this test have many false positives. Because of this, most physicians do not usually obtain this testing on their patients. It is great that you are routinely getting screened for STDs. One of the best ways to prevent transmission of disease is to always use condoms during sexual activity. Even one unprotected sexual encounter can lead to an unwanted sexually transmitted disease. You should follow up with your primary care physician to discuss your risks for STDs and Herpes and to review necessary testing.
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