Why You Have to Wait for an STD Blood Test

How antibody tests for herpes, HIV, and other STDs work

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Learning that you have been exposed to a sexually transmitted disease (STD) such as herpes or HIV can be frightening. It doesn't matter whether a former sexual partner calls to tell you they're infected or you hear from the health department that you need to be tested. It's scary to learn that you may be at risk.​

Although it's possible to test for some STDs, such as chlamydia and gonorrhea, relatively quickly after infection using a highly sensitive urine test, this is not the case with all STDs.

Any STD test that detects an infection using antibodies can't be used for at least several weeks. It may be six months or more before you can trust a negative result. The unfortunate truth is that STD results take time. 

Why You Have To Wait

Many STD tests, particularly those for viral STDs such as herpes and HIV, do not look for the infection itself. Instead, they look for your body's reaction to the infection, specifically your antibody response.

When you are exposed to or infected with an STD, your immune system will try to fight off the pathogen. Part of this process involves making antibodies against the infectious agent. These antibodies are specific to whatever you are infected with. That's how a blood test can look for antibodies to a specific STD and tell whether or not you have it. However, these specific antibodies take time to develop.

How much time it takes for you to make detectable amounts of antibodies against your infection depends upon a number of factors, including:

  • Whether you've been infected with the same pathogen before
  • How active the infection is
  • How much of the pathogen entered your body
  • The overall health of your immune system
  • What type of antibody the test is looking for

How Long Does an STD Blood Test Take?

The soonest a test might have a reasonable chance of detecting an antibody response is two weeks.

That is only true for tests that look for a specific early type of antibody called IgM. Many antibody tests look for IgG, which takes longer to develop. Furthermore, even an IgM test cannot be counted on to be accurate at such an early point after infection.

Within the first few months, there is a very high risk of false negative test results. This risk goes down over time. By six months after infection, most people will turn positive on an antibody test.

Because of this, antibody testing isn't appropriate for people who are worried they may have been very recently exposed to HIV or herpes. If this is the case, talk to your doctor about what type of testing may be right for you.

Once you get a test, the turnaround time for test results also varies. Some rapid STD tests can give results within an hour. Other STD results make take up to 1-2 weeks to come in. This varies both by what test is used and what facilities your doctor's office has. Some doctors need to send out blood and urine samples to be tested. Others can run the tests in-house. These factors can have a significant effect on STD results time. 

What Should You Do If You Just Can't Wait?

If you have a known, recent exposure to HIV, special testing may be available.

These acute tests are designed to detect a new infection. However, not all physicians will have access to these tests. They may need to send you to a more specialized clinic or lab.

If you think you have been exposed to herpes and you have symptoms, go to your doctor as soon as symptoms appear. Antibody tests take a while to become accurate. If your doctor can perform a viral culture on your sores, you can get results a lot sooner. For such a viral culture to work, your doctor has to be able to isolate the active virus from your sores. There is only a short window when that is possible after the beginning of an outbreak.

If you are tested after your sores have begun to heal, there is a possibility of a false negative test. However, your doctor may be able to give you a presumptive diagnosis based upon the appearance of your outbreak.

Sources:

Foster R, Ali H, Crowley M, Dyer R, Grant K, Lenton J, Little C, Knight V, Read P, Donovan B, McNulty A, Guy R. Does Living Outside of a Major City Impact on the Timeliness of Chlamydia Treatment? A Multicenter Cross-Sectional Analysis. Sex Transm Dis. 2016 Aug;43(8):506-12. doi: 10.1097/OLQ.0000000000000496.

Wong D, Berman SM, Furness BW, Gunn RA, Taylor M, Peterman TA. Time to treatment for women with chlamydial or gonococcal infections: a comparative evaluation of sexually transmitted disease clinics in 3 US cities. Sex Transm Dis. 2005 Mar;32(3):194-8.

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