Venereal Disease Research Laboratory slide test
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)
- Toddler test or procedure preparation (1 to 3 years)
- Preschooler test or procedure preparation (3 to 6 years)
- School age test or procedure preparation (6 to 12 years)
- Adolescent test or procedure preparation (12 to 18 years)
How the test will feel
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
Syphilis is a highly treatable infection. In addition to screening individuals with signs and symptoms of syphilis and/or other sexually transmitted diseases, syphilis screening is a routine part of prenatal care during pregnancy. Several states also require screening for syphilis prior to obtaining a marriage license.
The value of a negative test depends on the stage of syphilis that is suspected. Screening test is most valuable in secondary and latent syphilis as it will most likely be positive during these stages. During primary and tertiary syphilis this test may be falsely negative and additional testing may be needed prior to ruling out syphilis.
What abnormal results mean
A positive test result may indicate underlying syphilis. If the screening test is positive - the next step is to obtain a confirmatory test such as FTA-ABS which is more specific for syphilis as certain underlying illnesses can be associated with a positive test without actual infection with syphilis. These include HIV and other viral infections, mycoplasma pneumonia, lyme disease, and systemic lupus erythematosus or other autoimmune diseases.
What the risks are
Risks associated with venipuncture are slight:
- excessive bleeding
- fainting or feeling light-headed
- hematoma (blood accumulating under the skin)
- infection (a slight risk any time the skin is broken)
- multiple punctures to locate veins
This screening test for syphilis is usually performed on blood. If an individual is suspected of having brain involvement with syphilis (neurosyphilis), the VDRL test may be performed on spinal fluid.
by Dave R. Roger, M.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.