Syphilis is a sexually transmitted disease (STD) caused by a certain type of bacteria (called Treponema pallidum). This type of bacteria usually is spread during sexual contact (including kissing or oral sex).
A syphilis infection can spread through the bloodstream to all parts of the body. If not treated, syphilis can progress through three stages, usually extending over many years, to the point of affecting behavior. A syphilis test may be done to evaluate people with symptoms of dementia. The last stage of the disease can cause severe heart disease, brain damage, spinal cord damage, blindness, and death.
A pregnant woman with untreated syphilis can pass the infection to her fetus during pregnancy or birth (congenital syphilis). The risk of infecting the fetus is greatest when the mother is in the early stages of syphilis. However, fetal infection is possible any time during pregnancy when the mother is infected with syphilis.
If the pregnant woman receives treatment before the 16th week of pregnancy, the newborn usually will not have any signs of the illness and will not have syphilis in his or her blood. Untreated infection during pregnancy can cause miscarriage, premature birth, stillbirth, or birth defects in the fetus.
There are several methods used to test for syphilis:
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Venereal disease research laboratory (VDRL) test. The VDRL test is done to screen for syphilis. It checks for an antibody called reagin that can be produced in people who have syphilis. Reagin is not produced as a reaction to the syphilis bacteria specifically, so this test sometimes can be inaccurate. The VDRL test may be done on a sample of blood or spinal fluid. The VDRL test is not very useful for detecting syphilis in very early or advanced stages. |
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Rapid plasma reagin (RPR) test. The RPR test also detects reagin and is commonly used as a screening test. The RPR test is done on a sample of blood. It is not done on spinal fluid. |
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Fluorescent treponemal antibody absorption (FTA-ABS) test. The FTA-ABS test is more difficult to do and is not used as a screening test. It may be used to confirm a syphilis infection after a positive screening test. This test detects antibodies to the bacteria that cause syphilis and can be used to detect syphilis in all stages (except for the first 3 to 4 weeks). The test can be done on a sample of blood or spinal fluid. |
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Microhemagglutination assay (MHA-TP). The microhemagglutination assay for Treponema pallidum (MHA-TP) is used to confirm a syphilis infection after screening test results indicate syphilis. The MHA-TP test detects antibodies to the bacteria that cause syphilis and can be used to detect syphilis in all stages (except for the first 3 to 4 weeks). This test is not done on spinal fluid. |
Why It Is Done
A test for syphilis is done to:
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Screen for syphilis or monitor treatment for a syphilis infection (using the VDRL or RPR test). |
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Confirm that a syphilis infection is present (using the FTA-ABS or MHA-TP test). |
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Screen pregnant women for syphilis. Prenatal syphilis testing is required by law in all states. |
How to Prepare
Tell your doctor if you are taking any antibiotics. You may need to avoid eating and drinking for up to 10 hours before a syphilis test. You may also need to avoid drinking alcohol for 24 hours before the VDRL test, since alcohol may affect the test results.
If you may have syphilis, you should avoid sexual contact until the test results show you are not infected or until you have completed treatment and the infection has been cured.
How It Is Done
The person drawing blood will wrap an elastic band around your upper arm to temporarily stop the flow of blood through the veins of your arm. This makes it easier to place the needle into a vein properly because the veins below the band get larger and do not collapse easily.
The needle site is cleaned with alcohol and the needle is inserted. More than one needle stick may be needed if the needle does is not placed correctly or if the vein cannot supply enough blood.
When the needle is properly placed in the vein, a collection tube will be attached to the needle. Blood will flow into the collection tube. Sometimes more than one tube of blood is collected.
When enough blood has been collected, the band around your arm will be removed. A gauze pad or cotton ball is placed over the puncture site as the needle is withdrawn. Pressure is applied to the puncture site for several minutes and then a small bandage is often placed over it.
See the medical test topic Lumbar Puncture (Spinal Tap) for the method used to collect a spinal fluid sample.
How It Feels
You may feel nothing at all from the needle puncture, or you may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. However, many people do not feel any pain (or have only minor discomfort) once the needle is positioned in the vein. The amount of pain you feel depends on the skill of the person drawing the blood, the condition of your veins, and your sensitivity to pain.
See the medical test topic Lumbar Puncture (Spinal Tap) for how it feels to have a sample of spinal fluid collected.
Risks
There is very little risk of complications from having blood drawn from a vein. You may develop a small bruise at the puncture site. You can reduce the risk of bruising by keeping pressure on the site for several minutes after the needle is withdrawn.
Rarely, the vein may become inflamed after the blood sample is taken. This condition is called phlebitis and is usually treated with a warm compress applied several times daily.
Continued bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medications can also make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medication, tell the person before your blood is drawn.
See the medical test topic Lumbar Puncture (Spinal Tap) for the risks involved in collecting a spinal fluid sample.
Results
Results of syphilis testing are usually reported as:
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Nonreactive or negative if syphilis is not detected. These are normal results. |
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Reactive or positive if syphilis is detected. These are abnormal results. It takes about 4 to 6 weeks after exposure to syphilis for a blood test to be positive. |
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Reactive equivocal or inconclusive if the results are not clear. These are not clearly normal or abnormal results. |
A screening test (VDRL or RPR test) only detects the presence or absence of reagin. If a screening test is positive (reactive), the strength of the result may be determined by measuring the amount of reagin. The results are then given in titers. A titer is a measure of how much the blood or spinal fluid sample can be diluted before the reagin can no longer be detected.
A titer of 1 to 20 (1:20) means that reagin can be detected when 1 part of the blood or spinal fluid sample is diluted by up to 20 parts of a salt solution (saline). A larger second number means there is more reagin in the sample. Therefore, a titer of 1 to 80 indicates more reagin than a titer of 1 to 20.
The accuracy of testing often depends upon the stage of syphilis. Syphilis testing may need to be repeated if initial results are uncertain or if there is repeated exposure to syphilis (such as from repeated unprotected intercourse).
A reactive or positive test result does not always indicate syphilis. This is especially true of the syphilis screening tests (VDRL and RPR tests). Many other conditions can cause positive test results, including chickenpox, tuberculosis, systemic lupus erythematosus (SLE), mononucleosis, leprosy, malaria, hepatitis, Lyme disease, and rheumatoid arthritis.
What Affects the Test
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The use of antibiotics before having a syphilis test may cause falsely nonreactive or negative results. |
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A blood transfusion in the weeks before having a syphilis test, or pregnancy, may cause inaccurate test results. |
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Rough handling, contamination, or inadequate refrigeration of the blood or spinal fluid sample can cause inaccurate test results. |
What to Think About
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Fluid from a sore that may be caused by syphilis sometimes is collected and examined with a special type of microscope (dark-field microscope). If syphilis bacteria are present, they can be seen as corkscrew-shaped organisms moving across the microscope slide. This test is used mainly to diagnose syphilis in an early stage. |
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Many states require the VDRL screening test before a couple can get a marriage license. |
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Screening for syphilis and other sexually transmitted diseases (STDs) often is done for people who have more than one sexual partner. If you have syphilis, your sexual partner(s) should be notified and treated to prevent serious complications and to stop the spread of the disease. |
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With treatment, a positive syphilis test result becomes negative. |
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Many states require doctors to report all cases of syphilis to the local health department. In some states, doctors are also required to ask for the names and addresses of your recent sexual partners. If you have syphilis, the health department may contact you to ensure that you undergo treatment. If you give the names of your sexual partners to your doctor or the health department, they will be contacted in confidence by the health department and advised to have a test for syphilis. |
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