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The venereal disease research laboratory test (VDRL) is a blood test that can identify syphilis infections. Syphilis is one of the most common sexually transmitted infections (STIs).

A VDRL test measures antibodies that are often produced within one to two weeks after an infected person develops an initial sore. VDRL testing can be performed on blood or spinal fluid.

Serologic tests provide only indirect evidence of syphilis and may be reactive in the absence of clinical, historical, or epidemiologic evidence of syphilis. The VDRL usually becomes reactive within the first few weeks after infection, peaks during the first year, and then slowly declines, so that low titers (levels) are seen in late syphilis. It can revert to negative in the absence of treatment in about 25% of cases. 

What are the Symptoms of Syphilis?

The symptoms of syphilis can be mild to severe, depending on the extent of the infection. However, in some cases, syphilis may not cause any symptoms for several years.

The primary symptoms of syphilis include:

- A small, painless sore

- A skin rash that does not itch

- Swelling in the lymph nodes near the sore

The secondary symptoms of syphilis include:

- A red or reddish-brown non-itchy rash that spreads to the entire body, including the soles of the feet and palms of the hands

- Sore throat

- Patchy hair loss

- Muscle aches and headaches

- Weight loss

- Fever

- Genital, oral, and anal wart-like sores

- Fatigue

The tertiary symptoms of syphilis include:

- Damage to the blood vessels, joints, heart, bones, and liver

- Gummas or soft tissue swellings

Potential for false positives and negatives:

The VDRL test is not always accurate. For example, you may have false-negative results if you’ve had syphilis for less than three months, as it could take this long for your body to make antibodies. The test is also unreliable in late-stage syphilis.

On the other hand, the following can cause false-positive results:

- Lyme disease
- malaria
- pneumonia (certain types only)
- systemic lupus erythematosus
- IV drug use
- tuberculosis

In some cases, your body may not produce antibodies even if you have been infected with syphilis. This means the VDRL test will be inaccurate.

The antibodies produced as a result of a syphilis infection can stay in your body even after your syphilis has been treated. This means you might always have positive results on this test.

Potential treatment of Syphilis:

Syphilis is treatable if detected early. It's crucial to consult a doctor promptly if you suspect exposure to the infection. If left untreated, syphilis can spread throughout the body and lead to complications in various organs. Practicing safe sex is essential to prevent syphilis transmission, and seeking medical attention right away is vital if you suspect exposure to the infection.

The treatment strategy will depend on the symptoms and how long a person has harbored the bacteria. However, during the primary, secondary, or tertiary stage, people with syphilis typically receive an intramuscular injection of penicillin G benzathine.

Late latent and tertiary syphilis will typically require weekly injections for up to 3 weeks.

Neurosyphilis requires intravenous (IV) penicillin for 2 weeks to remove the bacteria from the central nervous system.

People with a penicillin allergy can sometimes use an alternative medication in the early stages. However, during pregnancy and in the tertiary stages, anyone with an allergy will undergo penicillin desensitization to allow for safe treatment.

Following delivery, newborn infants with syphilis should undergo antibiotic treatment.

Chills, fever, nausea, achy pain, and a headache may occur on the first day of treatment. Doctors refer to these symptoms as a Jarisch-Herxheimer reaction. It does not indicate that a person should stop treatment.


Nayak S, Acharjya B. VDRL test and its interpretation. Indian J Dermatol. 2012 Jan;57(1):3-8. doi: 10.4103/0019-5154.92666. PMID: 22470199; PMCID: PMC3312652.

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