Getting an STI test is a routine part of looking after your health, in the same way as checking cholesterol or blood pressure. Many people test when starting a new relationship, some test once a year, and others test after a specific worry. The harder part is often choosing which test, because the names on a catalogue can be confusing.
This guide explains the sexual health tests in the BPR catalogue, what each one covers, which sample it uses, and when testing usually makes sense.
Why test without symptoms?
Sexually transmitted infections are common. The NHS points out that many STIs have no symptoms, so you can have one without knowing, and that the only way to know for sure is to get tested (NHS, STIs). For chlamydia in particular, most people who have it do not notice any symptoms (NHS, Chlamydia).
A review in JAMA reported that a large share of herpes and trichomoniasis infections, and of gonorrhoea and chlamydia infections outside the genitals, cause few or no symptoms (Tuddenham et al., 2022). Testing is therefore about information, not about assuming something is wrong.
Two kinds of sample, two kinds of test
STI tests fall into two broad groups:
- Blood tests look for antibodies or antigens. They are used for HIV, syphilis, hepatitis B and hepatitis C.
- PCR tests on urine or a swab look for the genetic material of the organism itself. They are used for infections such as chlamydia and gonorrhoea. Nucleic acid amplification tests like these have high sensitivity (Tuddenham et al., 2022).
Most of the combined profiles below use both.
The options in the BPR catalogue
Full screens: Male and Female Sexual Health Advanced Screen
The Male Sexual Health - Advanced Screen and the Female Sexual Health - Advanced Screen cover the infections LML describes as the commonest: chlamydia, gonorrhoea, HIV, hepatitis B, hepatitis C and syphilis. The male version uses a blood sample and a first-catch urine sample. The female version uses a blood sample plus a self-taken swab, which LML prefers, or a urine sample. LML states that results are usually available one day after the samples reach the laboratory.
For most people looking for a single, broad check, this is the natural starting point.
Blood only: Sexual Health Bloods Only
The Sexual Health Bloods Only profile covers four blood markers: HIV 1 and 2 antibodies with p24 antigen, hepatitis C antibody, syphilis IgG/IgM and hepatitis B surface antigen. It does not include chlamydia or gonorrhoea, which need urine or a swab.
Wider PCR panel: Sexually Transmitted Infections by PCR
The Sexually Transmitted Infections by PCR test looks for seven organisms in one sample: chlamydia, gonorrhoea, Mycoplasma genitalium, Trichomonas vaginalis, Ureaplasma species and herpes simplex types 1 and 2. The sample can be first-catch urine, a swab, a ThinPrep vial or semen. LML reports an interim result first, with full results usually three days after arrival in the laboratory.
Single tests
- Chlamydia/Gonorrhoea (Urine) and Chlamydia/Gonorrhoea (PCR Swab): PCR for both infections, from urine or a swab.
- HIV I & II Antibody & p24 Antigen Test: a blood test that looks for antibodies to HIV types 1 and 2 and for the p24 antigen. Fourth-generation tests that look for p24 as well as antibodies shorten the window period compared with antibody-only tests (Lee et al., 2013).
- Syphilis TP (IgG/IgM): a blood test for antibodies to Treponema pallidum, the bacterium that causes syphilis. Blood tests remain the recommended way to investigate syphilis (Tuddenham et al., 2022).
Timing: when to test after sex
Timing matters as much as the choice of test. The NHS explains that STIs can take up to 7 weeks after unprotected sex to show up on a test, and that if you have no symptoms it is best to wait 7 weeks before testing (NHS, STIs). Testing earlier is possible, but a negative result may then need repeating.
There is one important exception. If you think you were exposed to HIV in the last 72 hours, go to a sexual health clinic or A&E, where emergency HIV medicine may be offered (NHS, HIV). That is a same-day matter, not a reason to order a test and wait.
