Exam VDRL: what is and how to understand the result (reactive and non-reactive)

El Examen VDRL, which means Venereal Disease Research Laboratory, is a blood analysis aimed at diagnosing and evaluating the response to treatment for syphilis, a sexually transmitted infection also known as lues. In this way, through the extraction of a sample of blood, which is sent to the laboratory for processing, it is possible to identify the presence of circulating antibodies and their concentration, indicating the severity of the illness.

Although the VDRL is one of the main methods for diagnosing syphilis, it may give a false positive result, because the person may have other diseases such as leprosy, tuberculosis or hepatitis, for example, which is why it should be carried out in together with other exams that also confirm the infection.

Syphilis is a sexually transmitted infection caused by bacteria Treponema pallidum, It is there that the presence of lesions in the genital region is verified that do not cause discomfort, and can go unnoticed many times. However, in case it is not identified or treated, the bacteria can remain in the body and cause the development of more serious forms of the disease, whose symptoms can be noticed after the initial infection.

See what are the symptoms of syphilis.

VDRL Exam

How the VDRL exam is performed

The VDRL test is carried out by means of a simple blood test, from which a small sample of the misma is extracted to be sent to the laboratory and analyzed. In the laboratory, the sample of blood is processed, added to a glass plate and mixed with reagents, dilutions are carried out in series with the objective of verifying the reaction, which indicates the severity of the illness.

It is common that the VDRL is carried out together with the RPR, which is also a test capable of identifying the presence of antibodies against bacteria circulating in the blood; no embargo, so like the VDRL, it is not specific to it Treponema pallidum, that it is the bacteria responsible for the infection, so in positive cases, treponemal tests can be performed, such as FTA-ABS and TP-PA, which are able to confirm that it is syphilis and differentiate it from past infections.

To carry out the exam, it is not necessary to carry out the exam, and the result is issued according to each laboratory, and can take from 24 hours to 7 days.

How to understand the result of the VDRL exam

Basically, the result of the VDRL exam can be:

• Positive or Reactive;
• Negative or Non-reactive.

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

The positive result generally indicates that the person has syphilis, however, there is also the possibility of having false positive results due to viral, bacterial, parasitic infections, hypersensitivity reactions or postvacunación, in these cases, it could mean that the person may have other diseases such as brucellosis, leprosy, hepatitis, malaria, asthma, tuberculosis, cancer and autoimmune diseases.

What does a positive result mean?

The result is considered positive when the dilution titer starts from 1/16. This title means that if the blood is diluted 16 times, it is even possible to identify antibodies, it is essential to consult a doctor in these cases so that the treatment can be started immediately.

Lower dilution titles 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 even dilutions it is possible to detect antibodies. As it is a possibility, it is important to go to the doctor to request a confirmation exam, since this title could be the result of a cross reaction, it is decir, a false positive.

Low titles are also found in primary syphilis, where antibodies circulate in blood at low concentrations and treatment is performed on certain occasions. In this way, in case the person has a history of syphilis, it is possible to present lower titles of the illness due to the persistence of the anti- bodies in the circulation; however, it is important that treponemic tests are carried out to verify whether this result is due to past infection or is indicative of an active infection, since there is no formation of immunity against it. Treponema pallidum.

VDRL exam in the embarazo

The VDRL examination in the embarazo must be carried out at the beginning of the prenatal period and must be repeated in the second trimester, if the result is negative, and the baby may have neurological problems if the mother has syphilis. Know which ones are the risks of syphilis in the embarazo.

If the result is positive, the embarazada can transmit the illness to the baby through the placenta or through the birth canal if the treatment is not followed correctly.

In case of diagnosis of syphilis in the pregnant woman, the VDRL exam must be carried out every month until the end of the embarazo to confirm that the bacteria causing syphilis is eliminated. Usually, the treatment of syphilis is carried out with the antibiotic penicillin, and derivatives of this antibiotic such as Amoxicillin, Ampicillin or Erythromycin are used in the embarazadas for 15 to 30 days. Find out more about the treatment for syphilis here.