VDRL / RPR (Syphilis Serology)
Also known as: Venereal Disease Research Laboratory Test, Rapid Plasma Reagin, RPR Titer, Syphilis Non-Treponemal Screen, STS Test
Parameters Measured in the Report
A breakdown of individual biomarkers and biological reference intervals typically found in your report:
| Biomarker | Standard Range | Unit | What It Means |
|---|---|---|---|
VDRL / RPR Reactivity (Non-Treponemal Screen) | Non-Reactive (Negative) | qualitative | Qualitative screen detecting reaginic antibodies against cardiolipin-cholesterol-lecithin antigen. |
RPR / VDRL Titer (Quantitative Titer) | Negative (If Reactive: reported as 1:1, 1:2, 1:4, 1:8, 1:16, etc.) | titer ratio | Highest serum dilution showing visible microscopic flocculation; tracks treatment response. |
* Note: Reference ranges may vary slightly between testing instruments and reagent kits. Always refer to the reference interval printed on your specific pathology report.
Clinical Focus
Circulating non-treponemal reaginic antibodies (IgM and IgG) directed against cardiolipin-lecithin antigens released from damaged host cells.
Sample & Specimen
Venous blood (Serum tube)
Fasting Protocol
No fasting required. Maintain regular water intake.
Turnaround Time
4–8 hours (same day)
What Is This Test?
Why Did Your Doctor Order This Test?
Physicians routinely prescribe the Syphilis (VDRL / RPR) in the following clinical scenarios:
How to Prepare Before Your Test
- No fasting or special preparation required.
Understanding Your Results
What higher or lower readings generally mean in clinical practice:
If Values Are Higher Than Normal
A Reactive VDRL/RPR titer indicates active primary, secondary, or early latent syphilis, but can also represent a Biological False Positive (BFP) caused by autoimmune diseases (Lupus/SLE), acute viral infections, pregnancy, or malaria. All reactive screens MUST be confirmed with a specific treponemal test (such as TPHA or FTA-ABS).
If Values Are Lower Than Normal
A Non-Reactive result indicates no detectable reaginic antibodies. In very early primary syphilis (before antibodies develop) or very late tertiary syphilis, reagin levels may be negative, requiring direct darkfield microscopy or specific treponemal PCR.
Frequently Asked Questions
Why do VDRL and RPR screening tests require a second confirmatory test?
Non-treponemal tests (VDRL/RPR) detect antibodies to cardiolipin (substances released by cellular damage) rather than the bacterium itself. Conditions like autoimmune lupus, pregnancy, or viral infections can cause false-positive results. Confirmatory treponemal tests (TPHA or FTA-ABS) check specifically for antibodies to Treponema pallidum.
How do doctors know if syphilis treatment has worked?
Doctors track quantitative RPR titers. A successful course of penicillin causes a fourfold (two-dilution) drop in titer (for example, falling from 1:32 down to 1:8 or lower) over 6 to 12 months.
Related Laboratory Tests
Tests frequently prescribed together or used as follow-up investigations:
HIV 1 & 2 (4th Generation p24 Antigen & Antibody Combo)
Simultaneous detection of HIV-1 p24 viral capsid antigen and host IgG/IgM antibodies against HIV-1 and HIV-2.
Hepatitis B Surface Antigen (HBsAg)
Qualitative and quantitative detection of Hepatitis B virus outer surface envelope protein in blood.
Complete Blood Count (CBC / Hemogram)
Counts and evaluates red blood cells, white blood cells, hemoglobin, hematocrit, and platelets.
Medical & Diagnostic Disclaimer
This guide is published for educational and patient informational purposes only. It is not a substitute for professional medical evaluation, diagnosis, or clinical advice.
A laboratory result that falls slightly outside standard statistical reference intervals does not automatically indicate disease; conversely, a normal result does not guarantee the absence of medical conditions. Only your attending physician can interpret lab findings in the context of your medical history, physical exam, and symptoms.