What Is Syphilis IgG?
Syphilis IgG is an antibody test used to screen for syphilis, a sexually transmitted infection caused by the spirochaete bacterium Treponema pallidum. IgG antibodies to T. pallidum develop within 2–4 weeks of infection and persist for life, even after successful treatment, making them useful for screening but not for distinguishing active from past treated infection.
Syphilis progresses through stages if untreated: primary (painless chancre), secondary (rash, mucous patches), latent (asymptomatic), and tertiary (cardiovascular and neurological damage). Early detection and treatment with penicillin is highly effective and prevents progression.
Why Is Syphilis IgG Tested?
- STI screening - recommended for new sexual partners, multiple partners, or symptoms
- Antenatal screening - all pregnant women in the UK are offered syphilis screening at booking
- Blood donation screening - mandatory for all blood donors
- Men who have sex with men (MSM) - annual screening recommended, more frequently if higher risk
- Genital ulcer investigation - painless ulcers (chancres) are characteristic of primary syphilis
- Contact tracing - partners of known cases should be tested
Interpreting Results
| Result | Interpretation |
|---|---|
| IgG negative | No evidence of current or past syphilis (or very early infection before seroconversion) |
| IgG positive | Current or past syphilis - requires confirmatory testing and clinical assessment |
A positive IgG screen is followed by RPR/VDRL (non-treponemal test) to assess disease activity. Treponemal antibodies (IgG) remain positive for life even after treatment; RPR/VDRL titres decline with successful treatment.
What Does a Positive Result Mean?
- Active syphilis - if RPR/VDRL is also positive, treatment is needed
- Past treated syphilis - IgG remains positive but RPR/VDRL should be negative or very low titre
- Latent syphilis - positive serology without symptoms; classified as early (<2 years) or late (>2 years)
- False positive - rare with specific treponemal tests but can occur in autoimmune conditions
Treatment
- Benzathine penicillin G - single intramuscular injection for early syphilis; weekly for 3 weeks for late syphilis
- Doxycycline - alternative for penicillin-allergic patients
- Partner notification - all sexual contacts should be informed and tested
- Follow-up — RPR/VDRL at 3, 6, and 12 months to confirm treatment success
- HIV testing — syphilis and HIV share risk factors and syphilis increases HIV acquisition risk
When Should You Get Tested?
- New sexual partner or unprotected sex
- Symptoms: painless genital ulcer, rash on palms/soles, mucous patches
- Pregnancy (routine antenatal screening)
- Annual screening for MSM
- After sexual assault or potential exposure
Check Your Syphilis IgG Levels at Home
The Core Health 45 includes Syphilis IgG testing along with 44 other biomarkers. Results in 2 working days with a free at-home phlebotomist visit.
View Core Health 45 →Which Lola Health Tests Include Syphilis?
Syphilis IgG screening is available as an add-on with any Lola Health blood test. For comprehensive STI screening, it can be paired with other relevant tests.
Check Your Syphilis Levels
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