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What is VDRL test?

VDRL stands for Venereal Disease Research Laboratory. VDRL test is a blood test performed to diagnose syphilis, an STD caused by the bacteria Treponema pallidum. Though a VDRL test does not screen for this bacteria, instead, it checks for the presence of anti-syphilis antibodies in blood. Antibodies are immune system proteins that your body makes to fight against harmful pathogens, in this case, the syphilis bacteria.

As it travels in the bloodstream, Treponema pallidum can easily spread to healthy individuals through direct contact with infected blood. The disease can also be transmitted from a mother to baby via placenta. Syphilis has the following three stages:

  • The primary stage, characterised by painless open sores at the point of contact, skin rash, body pain, and fever. It can last up to 6 months.
  • Secondary stage, in which the disease spreads throughout the body and  symptoms slowly start to disappear
  • Tertiary stage, characterised by the loss of muscle control. It can lead to personality changes, loss of memory and hallucinations.

In between the secondary and tertiary stage, there could be a latent stage, which is characteristically asymptomatic, though the presence of infection can be detected with the help of blood tests. Therefore, screening for syphilis is of importance for a person’s health and of those close to him/her.

  1. Why is a VDRL test performed?
  2. How do you prepare for a VDRL test?
  3. How is a VDRL test performed?
  4. What do VDRL test results mean?

Doctors order a VDRL test if they notice symptoms of syphilis in a person. 

A VDRL test is a part of routine tests for prenatal care and pregnancy in many countries. It is recommended for anyone who shows symptoms of any sexually transmitted illness.

The test may also be performed to check the progress of syphilis antibiotic treatment.

No special preparations are required for this test. Inform the doctor about any vitamin, herbal or medical supplements that you might be consuming. Your doctor also needs to be aware of the usage of any over-the-counter medication or illegal drugs. Medicines can affect blood test reports; therefore, it is essential that you do not change the course of any medication without informing your doctor first.

It is a simple test in which a blood sample is withdrawn from a vein in an arm. For this, a laboratory technician may first tie a tourniquet around your upper arm and clean a small area on the arm with an antiseptic solution. Next, they will use a needle to withdraw blood from a prominent vein. You may feel a slight pain due to the prick of the needle, but it will fades away soon.

The blood sample will be transferred to a clean sterilised tube and labelled with your name and it will be sent for testing.

The technician will put some cotton gauze at the site of the puncture to stop bleeding. Finally, the site will be covered with a bandage. A few people experience bruising at the site of puncture, but it generally subsides on its own.

Normal results:

Normal result for a VDRL test is negative. This result means that anti-syphillis antibodies were not found in the blood sample, which correlates with the absence of syphilis bacteria in the body.

However, VDRL test has a high proportion of false negatives when the disease has progressed to the tertiary phase or is in the early primary stage. 

Abnormal results:

The results are said to be abnormal when they are positive; it means that the antibodies against syphilis bacteria are present in your blood, which correlates to the presence of bacteria in the body. Positive results are usually seen in the secondary and latent phases. 

This test has a high frequency of false positives when the person is affected by other diseases, such as HIV, malaria, Lyme disease, certain pneumonia or systemic lupus erythematosus. So, it is crucial that the results of VDRL test are confirmed with other tests. Doctors generally order further tests to confirm positive VDRL results.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. The above information is provided from a purely educational point of view and is in no way a substitute for medical advice by a qualified doctor.

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References

  1. University of California San Francisco [Internet]. Benioff children hospital, San Francisco; VDRL
  2. Gerard J. Tortora, Bryan H. Derrickson. Principles of Anatomy and Physiology. 14th Edition; Wiley, 2013. [internet].
  3. American Academy of Family Physicians [Internet]. Leawood (KS); Resolving the Common Clinical Dilemmas of Syphilis
  4. Bibbins-Domingo K et.al. Screening for Syphilis Infection in Nonpregnant Adults and Adolescents: US Preventive Services Task Force Recommendation Statement. JAMA. 2016 Jun 7;315(21):2321-7. PMID: 27272583
  5. Nayak S, Acharjya B. VDRL test and its interpretation. Indian J Dermatol. 2012 Jan;57(1):3-8. PMID: 22470199
  6. Richard W. Dehn, David P. Asprey. Essential Clinical Procedures E-Book. 3rd edition; Elsevier Health Sciences, 2013