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Diagnostic Tests for Syphilis

Syphilis: Diagnostic Tests

The list of diagnostic tests mentioned in various sources as used in the diagnosis of Syphilis includes:

Home Diagnostic Testing

These home medical tests may be relevant to Syphilis:

Tests and diagnosis discussion for Syphilis:

There are three ways to diagnose syphilis: a doctor's recognition of its signs and symptoms; microscopic identification of syphilis bacteria; and blood tests. The doctor usually uses these approaches together to detect syphilis and decide upon the stage of infection.

To diagnose syphilis by identifying the bacteria, the doctor takes a scraping from the surface of the ulcer or chancre, and examines it under a special "darkfield" microscope to detect the organism itself. Blood tests also provide evidence of infection, although they may give false- negative results (not show signs of infection despite its presence) for up to three months after infection. False-positive tests also can occur; therefore, two blood tests are usually used. Interpretation of blood tests for syphilis can be difficult, and repeated tests are sometimes necessary to confirm the diagnosis.

The blood-screening tests most often used to detect evidence of syphilis are the VDRL (Venereal Disease Research Laboratory) test and the RPR (rapid plasma reagin) test. The false-positive results (showing signs of infection when it is not present) occur in people with autoimmune disorders, certain viral infections, and other conditions.

Therefore, a doctor will administer a confirmatory blood test when the initial test is positive. These tests include the fluorescent treponemal antibody-absorption (FTA-ABS) test that can accurately detect 70 to 90 percent of cases. Another specific test is the T. pallidum hemagglutination assay (TPHA). These tests detect syphilis antibodies (proteins made by a person's immune system to fight infection). They are not useful for diagnosing a new case of syphilis in patients who have had the disease previously because once antibodies are formed, they remain in the body for many years. These antibodies, however, do not protect against a new syphilis infection. In some patients with syphilis (especially in the latent or late stages), a lumbar puncture (spinal tap) must be done to check for infection of the nervous system.


Syphilis usually is treated with penicillin, administered by injection. Other antibiotics can be used for patients allergic to penicillin. A person usually can no longer transmit syphilis 24 hours after beginning therapy. Some people, however, do not respond to the usual doses of penicillin. Therefore, it is important that people being treated for syphilis have periodic blood tests to check that the infectious agent has been completely destroyed. Persons with neurosyphilis may need to be retested for up to two years after treatment. In all stages of syphilis, proper treatment will cure the disease, but in late syphilis, damage already done to body organs cannot be reversed.

Effects of Syphilis in Pregnant Women

It is likely that an untreated pregnant woman with active syphilis will pass the infection to her unborn child. About 25 percent of these pregnancies result in stillbirth or neonatal death. Between 40 to 70 percent of such pregnancies will yield a syphilis-infected infant.

Some infants with congenital syphilis may have symptoms at birth, but most develop symptoms between two weeks and three months later. These symptoms may include skin sores, rashes, fever, weakened or hoarse crying sounds, swollen liver and spleen, yellowish skin (jaundice), anemia, and various deformities. Care must be taken in handling an infant with congenital syphilis because the moist sores are infectious.

Rarely, the symptoms of syphilis go undetected in infants. As infected infants become older children and teenagers, they may develop the symptoms of late-stage syphilis including damage to their bones, teeth, eyes, ears, and brain.


The open sores of syphilis may be visible and infectious during the active stages of infection. Any contact with these infectious sores and other infected tissues and body fluids must be avoided to prevent spread of the disease. As with many other STDs, methods of prevention include using condoms during sexual intercourse. Screening and treatment of infected individuals, or secondary prevention, is one of the few options for preventing the advance stages of the disease. Testing and treatment early in pregnancy is the best way to prevent syphilis in infants and should be a routine part of prenatal care.


Developing better ways to diagnose and treat syphilis is an important research goal of scientists supported by the National Institute of Allergy and Infectious Diseases (NIAID). New tests are being developed that may provide better ways to diagnose syphilis and define the stage of infection.

In an effort to stem the spread of syphilis, scientists are conducting research on a vaccine. Molecular biologists are learning more about the various surface components of the syphilis bacterium that stimulate the immune system to respond to the invading organism. This knowledge will pave the way for development of an effective vaccine that can ultimately prevent this STD.

A high priority for researchers is development of a diagnostic test that does not require a blood sample. Saliva and urine are being evaluated to see whether they would work as well as blood. Researchers also are trying to develop other diagnostic tests for detecting infection in babies.

Another high research priority is the development of a safe, effective, single-dose oral antibiotic therapy for syphilis. Many patients do not like getting an injection for treatment, and about 10 percent of the general population is allergic to penicillin.

Recently, the genome of this organism has been sequenced. The sequence represents an encyclopedia of information about the organism. Clues as to how to diagnose, treat, and vaccinate against syphilis have been identified already and are fueling intensive research efforts in this ancient but intractable disease.

(Source: excerpt from Syphilis, NIAID Fact Sheet: NIAID)

Diagnosis of Syphilis: medical news summaries:

The following medical news items are relevant to diagnosis of Syphilis:


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