References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
Lab tests for syphilis and herpes use different methods because the infections are detected differently. Syphilis is diagnosed mainly through blood antibody tests (or sometimes swabs from active lesions). Herpes is best diagnosed by swabbing an active blister or ulcer for PCR testing. Blood antibody tests for herpes exist but are less reliable and less commonly used in the UK.
Here’s a clear comparison.
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Syphilis Lab Testing
| Test | What It Detects |
|---|---|
| Treponemal antibody test | Antibodies specific to syphilis bacteria |
| Non-treponemal test (RPR, VDRL) | Antibodies indicating active infection |
| PCR swab from chancre | Direct identification of bacteria |
| Dark-field microscopy | Specialist visualisation of bacteria |
How Syphilis Is Confirmed
- Initial screening with treponemal antibody test
- Confirmation with another treponemal test
- Quantitative non-treponemal test to assess active infection
- Combined results determine current vs past infection
Herpes Lab Testing
| Test | What It Detects |
|---|---|
| PCR swab | The virus itself from an active lesion |
| Viral culture | Live virus from lesion (less commonly used now) |
| Type-specific blood antibody | Past exposure to HSV-1 or HSV-2 |
How Herpes Is Diagnosed
- Swabbing an active lesion is most reliable
- Test sooner is better — accuracy drops as lesions heal
- Can identify HSV-1 vs HSV-2
- Blood tests are less reliable and less commonly recommended in the UK
Why the Difference?
- Syphilis causes a sustained antibody response — blood tests work well
- Herpes is episodic — blood tests don’t tell you when or where infection occurred
- Direct visualisation works better for herpes when lesions are present
When to Test
- Visible sores or lesions — get them swabbed promptly
- After a possible exposure — blood tests for syphilis at appropriate intervals
- Routine screening — syphilis blood test as part of standard STI panel
- Pregnancy — both tests considered as part of antenatal care
Where Tests Are Done
- NHS sexual health clinics
- Hospital labs
- Some home test kits offer syphilis blood testing
- Specialist labs for unusual situations
Treatment
- Syphilis — penicillin injection (curative)
- Herpes — antiviral medication (manageable, not curative)
Read more: What is syphilis? | What is herpes? | Syphilis confirmation tests
Frequently Asked Questions
Can I test for both at the same time?
Yes — syphilis blood and herpes lesion swab can be done at the same visit.
Why isn’t herpes blood testing offered routinely?
Results can be hard to interpret and don’t usually change management.
Is one swab enough for both?
Different samples are needed — blood for syphilis and a lesion swab for herpes.
Related reading
- Blood Test for Syphilis, Hepatitis B and Hepatitis C
- Cold Sores vs Syphilis Sores: How to Tell the Difference
- Multi-Site STI Testing: Genital, Rectal and Throat
- Can You Get Herpes From a Toilet Seat?
- Can You Get Herpes From Kissing?
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
