VDRL / RPR
The Venereal Disease Research Laboratory (VDRL) and Rapid Plasma Reagin (RPR) are non-treponemal tests used to screen for syphilis. They detect antibodies against lipoidal material released from damaged cells — not antibodies against the syphilis bacterium itself. A positive VDRL/RPR must always be confirmed with a treponemal-specific test (TPHA, FTA-ABS, or treponemal immunoassay). Titre changes after treatment indicate response — a four-fold drop indicates adequate treatment.
Expected Result
Normal
Non-reactive
A reactive VDRL is always confirmed with a treponemal test (TPHA, FTA-ABS). Biological false positives occur in pregnancy, autoimmune disease, and certain infections.
This is a qualitative test — results are reported as positive or negative rather than as a numeric range. Interpretation may vary by laboratory method; always review with your doctor.
What a Negative Result Means
A non-reactive VDRL generally rules out active syphilis. In primary syphilis the test may be falsely negative in the first 1–2 weeks of the chancre — repeat if clinical suspicion is high. In late latent or tertiary syphilis, VDRL sometimes reverts to negative even without treatment, so a non-reactive result with a positive treponemal test may still indicate treated or long-standing syphilis.
What a Positive Result Means
A reactive VDRL suggests syphilis but is not specific. Confirmation with TPHA or another treponemal test is essential. Biological false positives occur with pregnancy, autoimmune disease (especially SLE and antiphospholipid syndrome), chronic infections (malaria, TB, leprosy), and some vaccinations. A confirmed syphilis diagnosis triggers staging (primary, secondary, latent, tertiary) and appropriate benzathine penicillin treatment, along with partner notification.
Frequently Asked Questions
What is the difference between VDRL and TPHA?
VDRL is a non-treponemal test — sensitive for active disease, titres track disease activity and treatment response, but many false positives. TPHA (Treponema Pallidum Haemagglutination Assay) is a treponemal test — highly specific for syphilis infection past or present, but once positive it remains positive for life even after treatment. Both tests are complementary — VDRL plus TPHA is the standard two-step diagnostic algorithm.
Why might my VDRL be a biological false positive?
Pregnancy, autoimmune diseases (especially SLE and antiphospholipid syndrome), chronic infections (malaria, leprosy, TB, HIV), IV drug use, and some acute viral infections can produce non-specific reactivity. The key is the confirmatory treponemal test — a positive VDRL with a negative TPHA is a biological false positive and does not need syphilis treatment.
How is syphilis treatment followed up?
VDRL/RPR titres are rechecked at 6 and 12 months after treatment. A four-fold decline (for example 1:32 to 1:8) confirms adequate response. Persistent or rising titres suggest treatment failure or reinfection and require re-treatment. Treponemal tests remain positive for life and are not useful for monitoring response.
Related Infectious tests
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Antibody test for typhoid fever — used cautiously due to specificity issues.
InfectiousDengue NS1 Antigen
Early dengue virus antigen — detectable in the first week of fever.
InfectiousDengue IgM Antibody
Antibody that rises in the second week of dengue infection.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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