VDRL exam: what it is and how to understand the result

The VDRL exam, which meansVenereal Disease Research Laboratory, is a blood test used to diagnose syphilis, or lues, which is a sexually transmitted disease. In addition, this test can also be requested to monitor the disease in those who already have syphilis, which is a disease characterized initially by the presence of wounds in the region that does not hurt. See what are the symptoms of syphilis.

In some cases, examining syphilis may give a false positive result, which may mean that the person does not have syphilis, but may have other diseases, such as leprosy, tuberculosis or hepatitis, for example.

The VDRL exam must be performed before becoming pregnant and also every trimester of pregnancy, as it is a disease that can have serious health complications.

How the VDRL exam is performed

The VDRL exam is done through a simple blood test, in which a small blood sample is collected and analyzed in the laboratory.

Fasting is not necessary to perform the exam, although some doctors or laboratories indicate fasting for at least 4 hours to perform the exam. The test result is released according to the laboratory, and can be released within 24 hours or in 7 days.

Understanding the VDRL exam result

The result of the VDRL exam is given in titles: the higher the title, the more positive the test result is. Basically the result of the VDRL exam can be:

  • Positive or Reagent;
  • Negative or non-reactive.

If the result is negative, it means that the person has never come into contact with the bacteria that causes syphilis or is cured.

The positive result usually indicates that the person has syphilis, however there is also a possibility of having false-positive results due to the cross reactions that can happen and, in these cases, it may mean that the person may have other diseases such as brucellosis, leprosy, hepatitis, malaria, asthma, tuberculosis, cancer and autoimmune diseases.

What does the positive result mean

The result is considered positive when the title starts from 1/16. This title means that even by diluting the blood 16 times it is still possible to identify antibodies.

Lower titers, such as 1/1, 1/2, 1/4 and 1/8, indicate that it is possible to have syphilis, because after one, two, four or eight dilutions it was still possible to detect the antibodies. As it is a possibility, it is important to go back to the doctor so that a confirmatory exam is requested, as this title may be the result of a cross reaction, that is, a false positive. Low titers are also found in primary syphilis, where antibodies circulate in the blood at low concentrations.

Titles above 1/16 indicate that you have syphilis and, therefore, you should go to the doctor to start treatment quickly.

Watch the following video and learn about the symptoms, mode of transmission, diagnosis and treatment of syphilis:

VDRL examination in pregnancy

The VDRL exam in pregnancy must be performed at the beginning of prenatal care and must be repeated in the second trimester, even if the result is negative as the baby may have neurological problems if the mother has syphilis. See what are the risks of syphilis in pregnancy.

If the result is positive, the pregnant woman can transmit the disease to the baby through the placenta or the birth canal, otherwise the disease is not identified and treated correctly.

In case of diagnosis of syphilis in the pregnant woman, the VDRL test must be done every month until the end of the pregnancy in order to assess the woman's response to treatment and, thus, to be able to know if the bacterium that causes syphilis has been eliminated.

Usually syphilis is treated with Penicillin injections according to the gynecologist, obstetrician or infectious disease. Learn more about the treatment of syphilis, signs of improvement, worsening and complications.