STI Screening
Written 7th May 2020 - Last Update 31st August 2026
STI Screening
Most people carrying an STI have no symptoms, so screening is driven by a sexual history rather than by a presenting complaint.
Sexual history / risk assessment
Ask, in this order:
- When did you last have sex? Who have you had sex with in the last 3 months?
- Was that with a regular or a casual partner? Man, woman, or both?
- When did you last have vaginal, oral, or anal sex without a condom?
- Other than your regular partner, is there anyone else you’ve had sex with?
- In the past year, have you paid for sex, or been paid for sex?
- Have you ever been diagnosed with an STI?
Clinical pearls: make the sexual history a routine part of consultations, using a consistent script — don’t be deterred by an initially vague answer. Leave the “screening door open” (tell patients they can return if anything changes). Most people carrying a given STI are asymptomatic, including while transmitting it to others — symptom-triggered testing alone will miss most cases.
Who to check
Perform an asymptomatic STI check for people who request STI testing, are at increased risk (a new sexual partner, or living in or travelling to a higher-prevalence area in Australia or overseas), have a known exposure to any STI or a history of one in the past 12 months, or are the partner of someone in any of those groups.
Some subpopulations have special testing requirements because of increased risk of infection, adverse outcomes, or community prevalence: men who have sex with men, sex workers, pregnant people, Aboriginal and Torres Strait Islander people, and trans and gender diverse people.
Other risk markers worth acting on: more than 2 partners in the last 12 months, a partner with a known STI, HIV, injecting drug use, sexually active people under 30, and patients about to undergo a procedure where an undiagnosed STI raises complication risk (IUD insertion, termination of pregnancy).
The standard asymptomatic check-up
All STI testing should include both HIV and syphilis testing.
| Blood test | Consideration |
|---|---|
| HIV (antigen/antibody) | Repeat if recent exposure — 6-week window period for an Ag/Ab test |
| Syphilis serology | If recent exposure, repeat at 12 weeks and treat presumptively |
| Hepatitis B (HBsAg, anti-HBs, anti-HBc) | Establish status and immunise if not previously documented |
Routine adolescent hepatitis B immunisation started in Australia in 1997 and universal infant immunisation in May 2000, so people who grew up in Australia and were 34 or younger in 2020 can generally be assumed vaccinated and don’t need testing.
Gonorrhoea and chlamydia are tested by NAAT on first-pass urine or a self-collected vaginal swab. The vaginal swab is more sensitive than first-pass urine and is the specimen of choice; an endocervical swab can replace it if a speculum examination is indicated anyway.
Extragenital (pharyngeal and self-collected anorectal) swabs aren’t routine in women, but are indicated where risk is increased — sexual contacts of gonorrhoea or chlamydia, and sex workers. A positive gonorrhoea NAAT means recalling the patient for treatment and collecting culture for antibiotic sensitivity at that same visit.
What not to screen for when asymptomatic
- Hepatitis C — only with HIV, current PrEP use, injecting drug use, anal sex with a partner who has HCV, incarceration, non-professional tattoos or piercings, or blood products/organs received before 1990.
- Trichomonas — only in certain population groups and situations.
- Mycoplasma genitalium, bacterial vaginosis and HPV — not recommended. MSM and people living with HIV may still need HPV vaccination, as they may have missed school programs.
Discuss HIV PrEP where clinically appropriate, and provide condoms in the consultation.
Screening by population group
| Population | Test | Frequency |
|---|---|---|
| Young people 15–29 | Chlamydia | Annual |
| Hepatitis B | Confirm immunity, vaccinate if not immune | |
| Gonorrhoea/syphilis/HIV | Consider if high risk | |
| Asymptomatic people requesting screening | Chlamydia | Annual or more often |
| Hepatitis B | Confirm immunity, vaccinate | |
| HIV | Offer to everyone requesting testing | |
| Syphilis/gonorrhoea | Based on risk assessment and local prevalence | |
| Aboriginal or Torres Strait Islander people | Chlamydia/gonorrhoea/syphilis | At least annually |
| Hepatitis C/HIV | Low threshold, especially with other infections present | |
| Hepatitis B | Confirm immunity, vaccinate | |
| MSM / male sex workers | Chlamydia, gonorrhoea, syphilis, HIV | 3-monthly if any sex with a man in the last 3 months; annually if in a monogamous relationship |
| Hepatitis A/B | Test for immunity | |
| Hepatitis C | Only if HIV-positive or on PrEP | |
| Female sex workers | Chlamydia, gonorrhoea, syphilis, HIV | Based on risk assessment; more frequent if condom use isn’t consistent |
| Hepatitis A/B | Test for immunity | |
| Hepatitis C | Test for antibody | |
| People who inject drugs | Chlamydia/gonorrhoea/syphilis | Annual or more often |
| Hepatitis A/B | Confirm immunity, vaccinate | |
| HIV/hepatitis C | Annual | |
| Pregnant women | Syphilis, hepatitis B/C, HIV | At first antenatal visit |
| Chlamydia | If <30, or in high-prevalence areas | |
| Gonorrhoea | High-prevalence areas or risk factors present |
Syphilis as “the great pretender”
Worth flagging as a diagnostic principle: syphilis can mimic a wide range of dermatologic and systemic disease at the secondary/late stages, and patients often present with these diverse manifestations without recalling or having presented for an earlier stage of infection — keep it on the differential for unexplained rashes/systemic symptoms with any sexual-history risk factors, not only in patients who report a known exposure.
Australia has seen ongoing elevated syphilis notifications, particularly among MSM, but heterosexual men and women with risk factors (new or multiple partners, sex work) should not be overlooked. See Syphilis for staging and treatment detail.