Could I still have an STI if my results were all negative?
You got tested for STIs last week and all your results were negative.
But that guy you hooked up with a couple of weeks ago has just told you he tested positive for syphilis. You consider getting tested again, but it seems like overkill. You’ve got no symptoms, and if he’d passed it on to you, your tests would have picked it up, right?
Not necessarily. Welcome, brother, to the window period. Tests for syphilis, chlamydia, gonorrhea, and every other STI have one. Let’s dive in!
What is an STI window period?
For an explanation, we spoke to Dr Vincent Cornelisse, Sexual Health Physician at the Melbourne Sexual Health Centre (MSHC), who is also completing a PhD on the prevention of STIs.
“The window period is the time after an exposure to an STI, during which it may not show up on a test. The window period for every STI is different, mainly because we use different tests to detect them,” says Cornelisse.
“For example, the tests we currently use for gonorrhea and chlamydia — from urine samples and swabs — test for the DNA of those organisms themselves, and have quite short window periods,” he explains (see below for a list of STI window periods). “But the syphilis test is a blood test. There is no good way of directly looking for syphilis, so the test we use looks for your immune response to the infection, which takes a bit longer to show up. It also varies, because some people’s immune systems will react more quickly or more slowly, so the window period is longer to account for those individual differences.”
It’s important to note that this doesn’t make testing useless within the window period. “The window period only refers to the accuracy of a negative result,” says Cornelisse. “A positive result is still possible within the window period, and it would still be an accurate positive result.”
So, if I have no symptoms after the STI window period, do I still need to get tested?
Yes, it’s a good idea if you think you’ve been exposed to an STI. The window period refers to testing, not to the time it takes for STI symptoms to show.
“Just like your Scruff pics, your test results are an intimate glimpse of the recent past.”
“There are a lot of people with STIs who have no symptoms,” says Cornelisse. “Having no symptoms after a possible exposure doesn’t put you in the clear, even when you’ve passed the window period. We recommend that men who have sex with men get tested every three months if they have more than one partner. In addition, get tested if you’ve think you’ve been exposed, or if you’ve attended a ‘sex event’ — like group sex or sex parties — that you think might have put you in contact with STIs.”
After more info on getting tested? Here’s how!
How do window periods affect my STI test results?
Just like your Scruff pics, your STI test results are an intimate glimpse of the recent past.
“Say for example that you come in and get a test done for all STIs, and all your results are negative. What that means is that one week ago you didn’t have chlamydia and gonorrhea, six weeks ago you didn’t have syphilis, and so on. If you’ve acquired any of these infections since then, they may not show up yet,” says Cornelisse. “That’s one of the reasons it’s so important to get tested regularly.”
Can you test negative for an STI and still have it?
So, what happens if you test negative for STIs, but later find out you may have been exposed? Can you still have it?
So, to return to our example, a guy gets a call that he’s been exposed to syphilis, which has a window period of six weeks. He was exposed two weeks ago and had a negative test result since then. What should he do?
“He should go and get a syphilis test,” says Cornelisse. “He will usually have two options. Option one is to get treated at the same time as the test, on the presumption that he might have syphilis, and because the syphilis may not show up on the blood test. Option two is to test today, abstain from sex for six weeks and then come back and re-test when he is outside of the window period. Most guys choose option one.”
No surprises there. Cornelisse says this would be different for other STIs, though. “For gonorrhea, the test is a lot more sensitive, has a much shorter window period, and the result is available in one or two days, so we often just recommend the test and not necessarily the treatment straight away,” he says.
How do different tests affect the HIV window period?
There are currently two ways to test for HIV: the HIV antibody test method, and the HIV RNA test.
“In Australia, we use the fourth-generation antigen antibody combination test for HIV. Without getting too technical, this test is designed to be able to detect HIV at various stages of infection.”
“…it’s important to get tested regularly, get treated if necessary, and come back for retesting if your doctor recommends it.”
The RNA test (which you may have seen headlining the opening seconds of your favourite bareback porn) isn’t used routinely as part of a screening test in Australia. “We would use it in specific situations, which are quite rare, and it’s not part of the STI testing you’d normally get. It would make possibly a few days’ difference to the HIV testing window period.”
More about all forms of available HIV Testing in our Knowledge Hub.
What can you do if you’re not on PrEP, you’ve been exposed to HIV, and you’re still within the window period?
“It depends on the timing,” says Cornelisse. “If you’ve been exposed in the last 72 hours, make an urgent appointment with a health professional to start Post-Exposure Prophylaxis (PEP). PEP does need to be started within 72 hours, and preferably within 24 hours.”
If you’re outside the 72-hour period, then PEP is not a very effective option. “But it’s still worth getting an HIV test done,” explains Cornelisse. “Even though you’re within the window period, it doesn’t mean the test will be useless. A positive result is still possible, and if that’s the case you can get started on your treatment quickly. And if you’ve had a high risk of exposure and you’ve missed the boat with PEP, minimise your risk of passing HIV to your sexual partners until you have a definitive result, either by abstaining or by using condoms.”
What are the window periods for different STIs?
While there are researched-based guidelines, STIs don’t necessarily stick to a schedule, and new research and technology can change how testing works. That’s why it’s important to get tested regularly, get treated if necessary, and come back for retesting if your doctor recommends it.
With that in mind, the current STI window periods for testing in Australia are:
*For HIV rapid tests and HIV self test kits the window period is up to 12 weeks (3 months).
You can find sexual health testing services nearby and across Australia using our interactive map.