Which STIs to test for, and how each is sampled

Not every test is right for every person, and a good screen is matched to you rather than ordered as a generic bundle. This article sets out what a standard screen covers, what an extended panel adds, and why the type of contact you have had decides which sites are sampled. No judgement, no assumptions: the doctor asks what is needed to get the right tests, then orders those.

The standard screen

For most people, testing starts with the four most commonly screened infections:

• Chlamydia, by a NAAT test on urine or a swab.

• Gonorrhoea, by a NAAT test on urine or a swab.

• HIV, by a fourth-generation blood test.

• Syphilis, by a blood test.

NAAT stands for nucleic acid amplification test. In plain terms it looks for the organism's genetic material, which makes it very sensitive and able to detect infection earlier than older methods. Hepatitis B is added to the standard screen for anyone who has not been vaccinated against it, since vaccination makes that infection far less likely.

How the samples are taken

The method depends on the infection and on your anatomy:

• Chlamydia and gonorrhoea: a urine sample, or a swab. A self-taken vaginal swab is more sensitive than a urine sample and is the preferred option where relevant.

• HIV, syphilis and hepatitis: a blood sample, taken from a vein or by finger-prick depending on the test.

• Active sores or ulcers: a swab taken directly from the affected area.

Swabs can usually be self-taken, which many people find more comfortable than having a clinician do it. The doctor explains exactly what each sample involves before anything is done, and nothing happens without your say-so.

Why the type of sex changes the test

Urine and genital swabs only check the genital area. Chlamydia and gonorrhoea can also live in the throat and the rectum, and an infection there will be missed entirely by a urine test. So the sites we sample follow the type of contact you have had:

• A throat swab is added for anyone who has given oral sex.

• A rectal swab is added for anyone who has received anal sex.

• Testing all three sites together, throat, rectum and genitals, is standard where there has been contact at more than one site.

This is asked of everyone and mentioned matter-of-factly, not as a reaction to assumptions about you. It is simply how the infections behave, and skipping the question would mean missing infections. A urine-only screen in someone with a throat infection would read as a false negative, which is exactly what we are trying to avoid.

The extended panel

Beyond the standard four, some tests are added case by case, when symptoms, history or a specific concern make them useful. The doctor recommends these at the consultation rather than ordering them by default:

• Hepatitis B and hepatitis C, by blood test.

• Herpes simplex (HSV): a swab of an active sore, or a blood test for past exposure.

• Mycoplasma genitalium, by a urine sample or swab.

• Trichomonas, by a urine sample or swab.

HPV testing is available as a standalone service. Cervical screening is not offered at launch, and if you are due a smear the doctor will point you to where to have it.

Why not just test for everything

Testing for everything regardless of risk sounds thorough, but some tests, particularly blood tests for past herpes exposure, can produce results that cause worry without changing what you would actually do. A screen matched to your situation gives you clear, useful answers rather than a longer list of question marks. The doctor explains what each test will and will not tell you, so you can decide with full information.

The honest summary

A standard screen covers chlamydia, gonorrhoea, HIV and syphilis, with hepatitis B added if you are not vaccinated. The type of contact you have had decides whether the throat and rectum are sampled too. Extended tests are added when they genuinely add something. The aim is the right screen for you, not the longest possible list.

Ready to start?

If you want to move from reading to acting, the next step is a short, confidential assessment with one of our doctors. No judgement, no assumptions.

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