The Role of Serostatus in STD Testing

Serostatus is an important word to understand when you're talking about STD testing. Sero- is the medical prefix for blood (from serum). As such, your serostatus technically describes whether your blood tests positive for a disease, toxin, or other material of interest.

However, for STD testing, serostatus is often not used to describe not whether your blood tests positive for a pathogen. Instead, it describes whether you are making antibodies against a particular disease. Therefore, a lot of the time serostatus is not a marker for an active STD infection. It is a marker for whether you have been exposed to a particular STD. The two are often the same, but they are not identical. You can have antibodies against a disease without an active infection.

man getting STD blood test
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STD Blood Tests and Serostatus

Any STD blood test technically leads to the determination of a serostatus. However, that term is used less frequently when describing direct blood testing for a pathogen.

In contrast, people are often said to be seropositive or seronegative for diseases like HIV and herpes. They are considered seropositive when antibodies against those viruses are detected using herpes blood tests and HIV antibody tests. Seropositivity is a good indication of viral infection.

Specific anti-HIV or anti-herpes antibodies are relatively unlikely to be present in a person who has not been infected with the virus being tested for. However, testing for antibodies is not the same as directly identifying a virus through nucleic acid amplification or viral culture. It does not prove that the virus is present in the blood. 

The relationship between serostatus and infection status can also be difficult for people to pin down in certain other circumstances. With the VDRL test for syphilis, antibody levels vary strongly over the course of an infection. A person with a latent syphilis infection will sometimes show up as seronegative on a VDRL test even though they do have syphilis.

People who are concerned about HIV or have undergone repeated HIV testing may be more familiar with the term seroconversion than they are with the term serostatus. The words derive from the same root, however. Seroconversion can be described as going from a state of seronegativity to one of seropositivity.

Doctors are often particularly concerned about STD prevention methods when they are dealing with serodiscordant couples. These are couples where one person's serostatus is negative for an STD while their partner is seropositive. For example, suppressive therapy to reduce herpes transmission may be recommended for serodiscordant couples where one person has genital herpes. In some cases, pre-exposure or post-exposure prophylaxis may be indicated for serodiscordant couples where one partner has HIV.

Reliably practicing safe sex is also particularly important for couples who have discordant serostatus. This is true even if they're in a long-term relationship. People should continue to practice safe sex even after there has been a safe-sex mishap. Contrary to common belief, STDs are not automatically transmitted every time people have sex. Therefore, a single mistake does not necessarily lead to an infection. It still makes sense to be cautious afterward. 

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