Syphilis Flashcards
List non-treponemal tests (reagin antibodies) for syphilis
How are their results presented?
What is their utility in diagnosing syphilis?
- Rapid plasmin reagin (RPR)
- Venereal disease research laboratory (VDRL)
- Toluidine red unheated serum test (TRUST)
Quantifies amount of IgM and IgG antibody present and reflects disease activity.
Positive test results reported as a titre.
Used to monitor effectiveness of treatment.
Can have false negatives if immunocompromised or very early disease.
List treponemal tests for syphilis
How are their results presented?
What is their utility in diagnosing syphilis?
- T. pallidum particle agglutination assay (TPPA)
- T. pallidum enzyme immunoassay (TP-EIA)
- T. pallidum haemoagglutination assay (TPHA)
Presented as reactive or not reactive result.
QUALITATIVE test, detects antibodies directed against specific treponemal antigens.
Patients with positive test are usually positive for life so limited use with prior treated disease.
What testing regimen does the NZSHS recommend for diagnosing syphilis?
Screening with TP-EIA.
If reactive, followed with RPR and TPPA/TPHA as confirmatory tests.
What stages of syphilis are considered contagious?
Primary, secondary and latent.
After 24 months in latent period people are no longer infectious to sexual contacts but pregnant women can still pass infection on to unborn fetus
What is the NZSHS recommendation for treatment of uncomplicated syphilis (not in pregnancy)?
If contagious (primary, secondary, early latent): benzathine penicillin 1.8g IM STAT.
If non-infectious (late latent): benzathine penicillin 1.8g IM weekly for 3 weeks.
What other screening should occur in someone diagnosed with syphilis?
- STI screening
- HIV serology
- Hep A, B +/- C if risk factors
- Genital swab for HSV if ulcers present.
What are the contact tracing intervals for syphilis depending on stage of disease?
Primary: sx duration + 3 months
Secondary: sx duration + 6 months
Early latent: 12 months
Late syphilis: long term partners and children if index case female.
Outline follow-up after completing adequate treatment for primary, secondary or early latent syphilis
- Repeat serology at 3, 6 and 12 months.
- Cure: 4-fold (2 dilutions) drop in RPR titre
- Treatment failure: <4-fold (2 dilutions) drop in RPR titre within 6 months.
- Reinfection: 4-fold (2 dilutions) rise in RPR titre e.g. RPR rise from 1:2 to 1:8.
Refer to sexual health specialist if suspected failure or reinfection.
What is the risk of fetal infection with syphilis?
Highest risk for fetal infection within first 4 years of infection; negligible after 8 years.
Risk of adverse pregnancy outcome and congenital syphilis infection: Primary syph: 100% Secondary syph 100% Early latent: 80% Late latent 10%
If mother is treated during pregnancy, what is the risk of congenital syphilis?
1-2%.
Better outcomes if treatment before 28 weeks.
List the opportunities/indications for syphilis testing in pregnancy
- First antenatal bloods screening
- Symptoms of syphilis or sexual contact with syphilis
- Stillbirth >= 20 weeks
- Opportunistically if not had syphilis test this pregnancy
- At maternal request
- Repeat testing in high risk women at 28-32 weeks and birth.
What is the definition of early congenital syphilis?
What is the definition of late congenital syphilis?
Early congenital syphilis: within first 2 years of life
Late congenital syphilis: after first 2 years of life.
Interpret these syphilis test results:
EIA - reactive
TPPA - reactive
RPR - reactive
Confirmed syphilis infection
Interpret these syphilis test results:
EIA - reactive
TPPA - reactive
RPR - non-reactive
Past treated syphilis or latent infection OR very early infection
RPR can be negative in very early infection.
Interpret these syphilis test results:
EIA - reactive
TPPA - non-reactive
RPR - reactive
Biological false positive OR very early infection.
Repeat in 2 weeks.
Interpret these syphilis test results:
EIA - reactive
TPPA - non-reactive
RPR - non-reactive
Possible early primary, latent or false-positive.
Retest in 1 month.
Interpret these syphilis test results:
EIA - non-reactive
TPPA - not tested
RPR - not tested
No evidence of syphilis, or too early.
Retest in 1 month if strong suspicion based on clinical evidence.
Why is the interpretation of neonatal syphilis serology difficult?
There is passive transfer of maternal syphilis antibodies.
These may persist for 15 months and cause TPPA to be reactive.
What neonatal syphilis serology results can be interpreted as the neonate having congenital syphilis?
Non-treponemal test titre RPR 4-fold (2 dilutions) higher than maternal RPR at birth.
Persistently reactive TPPA after 18 months.
What neonatal syphilis serology results can be interpreted as excluding congenital syphilis?
In an UNTREATED neonate:
non-treponemal test (RPR, VRDL) becomes non-reactive before 6 months of age.
What is the NZSHS recommendation for treatment of EARLY syphilis in pregnancy?
Benzathine penicillin:
Up to 28 weeks gestation: 1.8g IM STAT.
Over 28 weeks gestation: 1.8g IM on day 1 and 8 (2 doses)
What is the NZSHS recommendation for treatment of LATE syphilis in pregnancy?
Benzathine penicillin 1.8g IM on day 1, 8 and 15 (3 doses).
If a dose is missed, full course needs to be repeated.
What is the NZSHS recommendation for treatment of neurosyphilis?
BenZYL penicillin (Penicillin G) 1.8g - 2.4g IV Q4H OR 10.8g-14.4g continuous IV infusion over 24 hours via OPIVA. Duration 10-14 days.
What is the alternative antibiotic for patients with penicillin allergy?
No alternative.
Patients should be admitted to hospital for desensitisation treatment.
