VDRL

Alternative names

Venereal Disease Research Laboratory slide test

Definition

This screening test for syphilis measures reaginic antibody. Reaginic antibodies are produced in syphilis as a result of the interaction of the bacteria which causes syphilis (Treponema pallidum) and one's own body.

This test is a useful screening tool for syphilis, yet its ability to detect syphilis depends on the stage of the disease. In the earliest stage of syphilis (primary syphilis) this test is positive approximately 60% of the time. Its usefulness increases with later stages such as secondary syphilis and latent syphilis where it may be positive 70-90% of the time; yet in the final stages (tertiary syphilis) this test is usually positive in only 60% of cases.
There are several conditions which may cause a false positive test - such as HIV, Lyme disease, mycoplasma pneumonia, malaria, and systemic lupus erythematosus. Therefore, this screening test if found to be positive must be confirmed by a more specific test for syphilis such as FTA-ABS.

How the test is performed

Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood).

A needle is inserted into the vein, and the blood is collected in an airtight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

Infant or young child:

The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test

Infants and children:

The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:

• infant test or procedure preparation (birth to 1 year)