Syphilis – Diagnostics – Overview of Information and Clinical Research

Syphilis diagnosis relies on recognizing symptoms that often hide in plain sight and confirming infection through specialized blood tests and physical examination. Early detection is crucial because this bacterial infection can be completely cured with simple treatment when caught early, but can cause severe damage to vital organs if left untreated for years.

Introduction: Who Should Get Tested and When

Anyone who is sexually active should consider getting tested for syphilis, especially if they notice unusual sores, rashes, or other symptoms. The challenge with syphilis is that many people carry the infection without knowing it because symptoms can be painless, mild, or easily mistaken for other conditions. This makes regular screening particularly important for people at higher risk.^[1]

You should seek diagnostic testing if you notice a painless sore on your genitals, mouth, or around your anus, even if it doesn’t hurt. Other warning signs include an unexplained rash, especially on your palms or the soles of your feet, swollen lymph glands, flu-like symptoms that don’t improve, or patchy hair loss. Because the first sore typically appears about three weeks after infection but can show up anywhere from 10 to 90 days later, you might not connect your symptoms to a sexual encounter that happened weeks or months ago.^[2]

Certain groups of people should get tested regularly even without symptoms. Gay men and other men who have sex with men are disproportionately affected by syphilis and should consider testing at least annually, or more frequently if they have multiple partners. Anyone with a new sexual partner, someone who has been diagnosed with another sexually transmitted infection, or people who inject drugs should also seek testing.^[1]

⚠️ Important

All pregnant people should be tested for syphilis at their first prenatal visit. Untreated syphilis during pregnancy can pass to the baby, causing severe health problems, stillbirth, or infant death. Testing and treatment during pregnancy can prevent these tragic outcomes.^[2]

If a sexual partner tells you they have been diagnosed with syphilis or another sexually transmitted infection, you should get tested immediately, even if you feel completely healthy. Similarly, if you recently had unprotected sex with a new partner or multiple partners, testing is advisable. Healthcare workers who may have accidentally come into contact with syphilis sores or lesions should also seek testing.^[3]

Classic Diagnostic Methods

Diagnosing syphilis requires a combination of physical examination and laboratory testing. No single test can definitively diagnose syphilis on its own, which is why healthcare providers use multiple approaches to confirm the infection and determine what stage it has reached.^[9]

Physical Examination

Your healthcare provider will begin by examining your body for visible signs of syphilis. During the primary stage, they will look for a chancre, which is a firm, round, painless sore that typically appears where the bacteria entered your body. These sores can develop on the penis, vagina, anus, rectum, lips, or inside the mouth. Because chancres are painless, many people don’t notice them, and they may be hidden in areas that are difficult to see yourself.^[1]

If you are in the secondary stage, the doctor will look for a distinctive rash that often appears on the palms of your hands and soles of your feet. This rash is usually rough, red, or reddish-brown in color and typically doesn’t itch. The provider will also check for white or gray wart-like growths on your genitals or anus, white patches in your mouth, swollen lymph nodes, and signs of patchy hair loss on your head, beard, or eyebrows.^[3]

For suspected cases of neurosyphilis (when syphilis affects the brain and nervous system), ocular syphilis (affecting the eyes), or otosyphilis (affecting the ears), the examination becomes more specialized. The provider may check for severe headaches, muscle weakness, confusion, vision changes, eye pain, hearing loss, or dizziness. These conditions can occur at any stage of syphilis and require immediate attention to prevent permanent damage.^[1]

Blood Tests

Blood testing is the most common method for diagnosing syphilis, especially when there are no visible symptoms. A healthcare provider needs to use two different types of blood tests together to make a presumptive diagnosis of syphilis. These are called nontreponemal tests and treponemal tests.^[9]

Nontreponemal tests look for substances that your body produces in response to cell damage caused by syphilis bacteria. The two main types are the VDRL test (Venereal Disease Research Laboratory test) and the RPR test (Rapid Plasma Reagin test). These tests are useful for screening and monitoring treatment progress because the levels they measure typically decrease after successful treatment. However, they can sometimes show positive results for reasons other than syphilis, which is why a second type of test is always needed.^[9]

Treponemal tests look for antibodies that your immune system specifically creates to fight the syphilis bacteria (Treponema pallidum). These include tests like the TP-PA assay (T. pallidum passive particle agglutination), various enzyme immunoassays, chemiluminescence immunoassays, immunoblots, and rapid treponemal assays. Once you have been infected with syphilis, treponemal tests usually remain positive for life, even after successful treatment. This means they confirm that you have been exposed to syphilis at some point, but don’t necessarily indicate an active infection.^[9]

Blood tests can detect syphilis at all stages of infection. They are particularly valuable during the latent stage, when there are no visible signs or symptoms but the infection is still present in your body. The Centers for Disease Control and Prevention recommends using the RPR-based screening algorithm, especially in settings where there is a high probability of syphilis.^[9]

Direct Detection Methods

When sores or lesions are present, healthcare providers can examine fluid or tissue directly from these areas. Darkfield microscopy is a definitive method for diagnosing early syphilis. In this test, a healthcare provider collects fluid from a chancre or other syphilis lesion and examines it under a special microscope that can actually see the spiral-shaped syphilis bacteria moving. This test provides immediate confirmation of active infection.^[9]

A swab that looks like a cotton bud may be used to collect fluid from sores on your penis, vagina, anus, mouth, or other affected areas. Some laboratories also offer molecular tests that use PCR technology (polymerase chain reaction) to detect syphilis DNA directly from lesion samples or tissue. While these molecular tests are not commercially available everywhere, they are highly accurate when performed by specialized laboratories.^[9]

Cerebrospinal Fluid Testing

When doctors suspect that syphilis has affected your nervous system, they may need to test the cerebrospinal fluid, which is the liquid surrounding your brain and spinal cord. This is done through a procedure called a lumbar puncture or spinal tap. A needle is carefully inserted between two bones in your lower back to collect a small sample of this fluid.^[10]

Cerebrospinal fluid testing is strongly recommended for patients with tertiary syphilis, anyone showing neurological symptoms like severe headaches or confusion, people with vision or hearing problems that might be caused by syphilis, and patients whose blood test levels don’t decrease properly after treatment. This test helps determine whether syphilis bacteria have invaded the central nervous system, which requires different and more intensive treatment.^[9]

At-Home Testing Options

Some people can now use at-home syphilis test kits that you can order online or purchase from pharmacies. These kits typically involve collecting a small blood sample from your finger using a lancet, then sending it to a laboratory for analysis. While these tests can be convenient and private, any positive result must be confirmed with a healthcare provider who can arrange proper treatment and follow-up testing.^[10]

⚠️ Important

Rapid tests that provide results in just a few minutes are now available at many sexual health clinics. These point-of-care tests allow treatment to begin during the same clinic visit, which greatly improves outcomes and prevents transmission to others.^[5]

Diagnostics for Clinical Trial Qualification

While specific information about diagnostic criteria used for enrolling patients in syphilis clinical trials was not provided in the available sources, standard diagnostic methods described above would typically be required to confirm infection status before participation. Blood tests measuring both nontreponemal and treponemal antibodies would establish baseline infection levels, and additional testing might document the stage of syphilis present.

Patients entering trials might need documented proof of their syphilis diagnosis through positive results on both types of blood tests. The stage of infection would need to be clearly identified, as different trials might focus on primary and secondary syphilis versus latent or late-stage disease. Testing for HIV status is often included since syphilis and HIV frequently occur together, and HIV infection can affect how syphilis progresses and responds to treatment.^[3]

For trials testing new treatments, baseline measurements of antibody levels through nontreponemal tests would be essential for later comparison to determine treatment effectiveness. Participants might also need cerebrospinal fluid testing if the trial involves neurosyphilis treatment, or specialized eye examinations for ocular syphilis studies. Regular follow-up testing at specific intervals would be built into trial protocols to monitor treatment response and document cure rates.^[9]

Prognosis and Survival Rate

Prognosis

The outlook for people with syphilis depends almost entirely on how early the infection is detected and treated. When syphilis is found and treated during the primary or secondary stages, the prognosis is excellent. Early syphilis can be completely cured, sometimes with just a single injection of penicillin, preventing any long-term health consequences.^[2]

If syphilis advances to the latent stage without treatment, it can remain in your body for up to 20 years, slowly causing damage to your heart, bones, nerves, and organs. About 20% of people with untreated syphilis eventually progress to the late or tertiary stage, which brings serious and often irreversible complications. These can include brain damage, dementia, heart disease, movement disorders, nerve damage, seizures, and vision problems including blindness.^[3]

Tertiary syphilis typically develops 10 to 30 years after the initial infection in people who never received treatment. At this advanced stage, the disease has caused permanent damage to internal organs and can ultimately result in death. However, it’s important to understand that most people with untreated syphilis do not actually develop tertiary disease. The infection may remain in the latent stage indefinitely, or symptoms may be too mild to notice.^[1]

For babies born with congenital syphilis, the prognosis varies depending on how early in pregnancy the mother was infected and whether she received treatment. Untreated syphilis in pregnancy results in adverse birth outcomes in 50 to 80% of cases, including stillbirth, newborn death, and babies born with serious health problems. Surviving infants may face lifelong medical issues including developmental delays, seizures, blindness, deafness, and bone problems.^[5]

Survival rate

Specific survival statistics for syphilis were not extensively detailed in the available sources, but the World Health Organization reports that syphilis resulted in approximately 107,000 deaths globally in 2015. The vast majority of these deaths occurred in people with late-stage, untreated syphilis who developed severe complications affecting the heart, brain, or other vital organs.^[7]

With modern antibiotic treatment, death from syphilis is now rare in countries with access to healthcare. The bacteria remain highly sensitive to penicillin, and treatment can prevent progression to life-threatening complications when administered before permanent organ damage occurs. However, any damage already caused by untreated syphilis before treatment begins cannot be reversed. This is why early detection and prompt treatment are so crucial for ensuring the best possible outcome.^[8]

For pregnant individuals with syphilis who receive proper treatment during pregnancy, the prognosis for their babies is generally good. Testing and treating syphilis in pregnant people prevents the tragic outcomes associated with congenital syphilis, allowing most babies to be born healthy.^[2]

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