VDRL (RPR)

VDRL and RPR are non‑treponemal blood tests that screen for syphilis by detecting nonspecific “reagin” antibodies produced in response to tissue damage from Treponema pallidum. They’re used for initial screening and for monitoring treatment by measuring quantitative titers. False positives can occur with other infections, autoimmune conditions, or pregnancy, so positive results are confirmed with specific treponemal tests.

Positive VDRL means a non‑treponemal blood test detected antibodies (anti‑cardiolipin) commonly seen with syphilis. It suggests possible active or recent infection but can be a false positive in pregnancy, autoimmune disease, other infections, or after vaccination. A reactive VDRL needs clinical correlation and confirmation with a treponemal‑specific test (e.g., TPPA/FTA‑ABS) and may prompt treatment or follow‑up titers.

RPR (Rapid Plasma Reagin) is a non-treponemal blood test used to screen for syphilis by detecting reagin antibodies produced in response to cellular damage. It’s useful for initial screening and monitoring treatment by measuring titers. False positives can occur with other infections, autoimmune disease, or pregnancy, so positive RPR results require confirmatory treponemal testing.

The normal RPR (Rapid Plasma Reagin) result is nonreactive (negative); there should be no detectable RPR antibodies. Quantitative reports list titers—normal is undetectable or below the lowest dilution (e.g., <1:1). A reactive (positive) RPR with a measurable titer indicates possible syphilis and requires confirmatory treponemal testing and clinical correlation. Discuss results with your clinician for interpretation.

RPR is generally preferred for routine screening and treatment monitoring because it is simpler, faster, easier to automate and provides quantitative titers. VDRL performs similarly but is commonly used for cerebrospinal fluid testing in suspected neurosyphilis. Neither test is definitive; positive non-treponemal results require confirmation with a specific treponemal assay, and both can give false positives.

If RPR is positive, confirm with a treponemal test (e.g., TPPA/FTA‑ABS) and assess clinical stage. Test for HIV and other STIs. Treat promptly—benzathine penicillin G per stage; in pregnancy give immediate penicillin (desensitize if allergic). Notify and test recent sexual partners. Monitor treatment response with quantitative RPR titers; expect a fourfold titer decrease by 6–12 months.