Syphilis Testing Algorithms Using Treponemal Tests for Initial Screening --- Four Laboratories, New York City, 2005--2006 (2023)

Syphilis Testing Algorithms Using Treponemal Tests for Initial Screening --- Four Laboratories, New York City, 2005--2006 (1)

Syphilis Testing Algorithms Using Treponemal Tests for Initial Screening --- Four Laboratories, New York City, 2005--2006 (2)

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In the United States, testing for syphilis traditionally has consisted of initial screening with an inexpensive nontreponemal test, then retesting reactive specimens with a more specific, and more expensive, treponemal test. When both test results are reactive, they indicate present or past infection. However, for economic reasons, some high-volume clinical laboratories have begun using automated treponemal tests, such as automated enzyme immunoassays (EIAs) or immunochemoluminescence tests, and have reversed the testing sequence: first screening with a treponemal test and then retesting reactive results with a nontreponemal test. This approach has introduced complexities in test interpretation that did not exist with the traditional sequence. Specifically, screening with a treponemal test sometimes identifies persons who are reactive to the treponemal test but nonreactive to the nontreponemal test. No formal recommendations exist regarding how such results derived from this new testing sequence should be interpreted, or how patients with such results should be managed. To begin an assessment of how clinical laboratories are addressing this concern, CDC reviewed the testing algorithms used and the test interpretations provided in four laboratories in New York City. Substantial variation was found in the testing strategies used, which might lead to confusion about appropriate patient management. A total of 3,664 (3%) of 116,822 specimens had test results (i.e., reactive treponemal test result and nonreactive nontreponemal test result) that would not have been identified by the traditional testing algorithms, which end testing if the nontreponemal test result is nonreactive. If they have not been previously treated, patients with reactive results from treponemal tests and nonreactive results from nontreponemal tests should be treated for late latent syphilis.

Four New York City laboratories that routinely conduct syphilis testing using EIA treponemal screening tests were able to provide their testing algorithms, test volume, and test results for a convenience sample of specimens. Each laboratory used a slightly different testing algorithm and tested approximately 26,000--130,000 specimens for syphilis per year. CDC reviewed test results from a convenience sample of 116,822 specimens tested at these four laboratories during October 1, 2005--December 1, 2006.

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In all four laboratories, no further testing was done on specimens that were nonreactive with the treponemal screening EIA. In all four laboratories, specimens considered reactive by EIA test were next tested with a rapid plasma reagin (RPR) test. However, the approach to follow-up testing then differed. At two laboratories, specimens that were reactive with EIA and nonreactive with RPR were retested using a different treponemal test: Treponema pallidum particle agglutination (TP-PA) or fluorescent treponemal antibody (FTA-ABS). At a third laboratory, specimens that were reactive to both the EIA test and the RPR test were retested using a different treponemal test (i.e., FTA-ABS or TP-PA). At the fourth laboratory, no further testing was done after the EIA and RPR tests.

Of the 116,822 specimens included in the convenience sample, 6,587 (6%) were initially reactive to the EIA test (Figure). When 6,548 of the EIA-reactive specimens were tested with an RPR test, 2,884 (44%) were reactive and 3,664 (56%) were nonreactive to the RPR test. Further testing with FTA-ABS or TP-PA tests on 2,512 of the specimens reactive to the EIA test but nonreactive to the RPR test found 2,079 (83%) specimens reactive to the second treponemal tests (i.e., FTA-ABS or TP-PA). In addition, the one laboratory that performed TP-PA testing on specimens that were reactive to both the EIA and RPR tests found 78 of 80 (98%) specimens were reactive to the TP-PA test.

One laboratory provided limited interpretation of the various permutations of syphilis test results. The other three laboratories gave providers an objective summary of the test results (e.g., EIA reactive, RPR reactive, or EIA reactive and RPR nonreactive) with no interpretation. No additional information was available from the four laboratories regarding patient treatment.

Reported by: T Peterman, MD, J Schillinger, MD , S Blank, MD, S Berman, MD, R Ballard, PhD, D Cox, PhD, R Johnson, MD, S Hariri, PhD, N Selvam, PhD, Div of STD Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, CDC.

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Editorial Note:

In the four New York City laboratories studied, reversing the traditional order of screening and confirmatory tests for syphilis resulted in 3,664 (3%) of 116,822 specimens with test results (i.e., reactive treponemal test result and nonreactive nontreponemal test result) that would not have been identified by the traditional testing algorithm. The importance of these test results is unclear because no specific prognostic information exists to guide patient evaluation and treatment.

Treponemal tests detect antibodies specific to T. pallidum. In addition to T. pallidum pallidum, which causes syphilis, other treponemal subspecies (e.g., pertenue, which causes yaws, and carateum, which causes pinta) also can produce reactive results to treponemal tests, but these subspecies are rare in the United States (1). A reactive treponemal test result indicates that treponemal infection has occurred at some point in the past but cannot distinguish between treated and untreated infections. As such, treponemal tests, such as the T. pallidum EIA test, TP-PA test, and FTA-ABS test, can produce reactive results for life, even after adequate treatment for syphilis.

Nontreponemal tests, such as the RPR test and venereal disease research laboratory (VDRL) test, detect antibodies to cardiolipin and are not specific for treponemal infection. Nontreponemal tests are more likely than treponemal tests to produce nonreactive results after treatment; therefore, reactive results from nontreponemal tests are more reliable indicators of untreated infection. Quantitative nontreponemal tests also are used to monitor responses to treatment or to indicate new infections. False-positive nontreponemal tests occur in 1%--2% of the U.S. population, and have been associated with multiple conditions, including pregnancy, human immunodeficiency virus (HIV) infection, intravenous drug use, tuberculosis, rickettsial infection, spirochetal infection other than syphilis, bacterial endocarditis, and disorders of immunoglobulin production (2,3). Nontreponemal test results might be falsely negative in longstanding latent infection (4). Both treponemal and nontreponemal tests can produce nonreactive results when the infection has been acquired recently; approximately 20% of test results are negative when patients have primary syphilis (4).

The four New York City laboratories in this report used various algorithms to evaluate specimens that were reactive to treponemal tests and nonreactive to nontreponemal tests. The different algorithms might lead to confusion in the interpretation of test results and, in turn, in the management and treatment of patients. Test results that would not have been identified by the traditional algorithm were obtained for 3% of the specimens tested for syphilis; thus, such results might be expected to occur several thousand times per year in New York City alone.

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When results are reactive to both treponemal and RPR tests, persons should be considered to have untreated syphilis unless it is ruled out by treatment history. Persons who were treated in the past are considered to have a new syphilis infection if quantitative testing on an RPR test or another nontreponemal test reveals a four fold or greater increase in titer (health departments maintain registries of past positive tests). When results are reactive to the treponemal test but nonreactive to the RPR test, persons with a history of previous treatment will require no further management. For persons without a history of treatment, a second, different treponemal test should be performed (5). If the second treponemal test is nonreactive, the clinician may decide that no further evaluation or treatment is indicated, or may choose to perform a third treponemal test to help resolve the discrepancy.

If the second treponemal test is reactive, clinicians should discuss the possibility of infection and offer treatment to patients who have not been previously treated. Unless history or results of a physical examination suggest a recent infection, such patients are unlikely to be infectious and should be treated for late latent infections, even though they do not meet the surveillance case definition (7). Treatment can prevent severe (i.e., tertiary) complications that can result from untreated syphilis, although the probability of such complications occurring without treatment, while unknown, likely is small (6) Treatment also allows patients to report that they have been treated for syphilis if they ever receive similar results from future treponemal screening tests. Public health departments determine their own priorities for partner notification and other prevention activities; however, because late infections are unlikely to be infectious, they would likely be considered low priority for health department intervention activities.

Reversal of the traditional syphilis screening sequence has been driven by economics. For high-volume laboratories, an automated treponemal test can be less expensive than using an RPR test for the initial screening. An important consequence of this reversal is the identification of a combination of reactive and nonreactive test results that would not otherwise have been identified. The clinical interpretation of these results is complicated by the lack of standardized follow-up testing algorithms among the four laboratories, and by the lack of an evidence base with which to judge the merits of each algorithm. Consequently, use of a reversed sequence of syphilis testing might result in overdiagnosis and overtreatment of syphilis in some clinical settings.

The recommendations in this report might not be appropriate in countries with different patterns of seroreactivity, systems of health care, and epidemiology of disease. Furthermore, additional analyses are needed that further elucidate the use and total costs of these alternative screening approaches for syphilis, given the anticipated increase in use of treponemal tests for screening in the United States.

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  1. Egglestone SI, Turner AJ. Serological diagnosis of syphilis. PHLS Syphilis Serology Working Group. Commun Dis Public Health 2000;3:158--62.
  2. Hernandez-Aguado I, Bolumar F, Moreno R, et al. False-positive tests for syphilis associated with human immunodeficiency virus and hepatitis B virus infection among intravenous drug abusers. Valencian Study Group on HIV Epidemiology. Eur J Clin Microbiol Infect Dis 1998;17:784--7.
  3. Golden MR, Marra CM, Holmes KK. Update on syphilis: resurgence of an old problem. JAMA 2003;290:1510--4.
  4. Larsen SA, Steiner BM, Rudolph AH. Laboratory diagnosis and interpretation of tests for syphilis. Clin Microbiol Rev 1995;8:1--21.
  5. CDC. Sexually transmitted diseases treatment guidelines. MMWR 2006;55(No. RR-11).
  6. Wöhrl S, Geusau A. Neurosyphilis is unlikely in patients with late latent syphilis and a negative blood VDRL-test. Acta Derm Venereol 2006;86:335--9.
  7. CDC. Sexually transmitted disease surveillance, 2006. Atlanta, GA: US Department of Health and Human Services, CDC, 2007. Available at

Syphilis Testing Algorithms Using Treponemal Tests for Initial Screening --- Four Laboratories, New York City, 2005--2006 (3)
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Syphilis Testing Algorithms Using Treponemal Tests for Initial Screening --- Four Laboratories, New York City, 2005--2006 (4)


Which algorithm should be used to screen for syphilis? ›

The reverse sequence syphilis screening (RSSS) algorithm first uses a treponemal assay as a screen, followed by confirmatory testing of reactive samples with a non-treponemal test.

What is treponemal screening test for syphilis? ›

Treponemal tests, also called confirmatory tests (FTA, TP-PA, EIA), detect antibodies specific to syphilis. Treponemal antibodies will appear earlier after acute infection than non-treponemal antibodies. The antibodies detected in these tests usually remain detectable for life even after successful treatment.

What is the initial screening for syphilis? ›

Syphilis Serology. Serologic tests for syphilis require the use of two tests: nontreponemal tests that use a nonspecific cardiolipin antigen and confirmatory tests that use specific T. pallidum antigens (Table 1). A nontreponemal test, such as VDRL or RPR, may be used for screening.

What is the most accurate syphilis test? ›

The FTA-ABS test will help distinguish between syphilis and other infections or conditions. How well the RPR test can detect syphilis depends on the stage of the infection. The test is most sensitive (almost 100%) during the middle stages of syphilis.

What is the most accurate diagnostic test for syphilis? ›

The SpiroTek syphilis test has the highest sensitivity of all treponemal tests (especially in untreated primary syphilis) and is recommended as a confirmatory test by the CDC (1).

How accurate is syphilis treponemal test? ›

001), but no difference among low-risk MSM. Treponemal and nontreponemal tests were accurate in asymptomatic individuals (sensitivity >85%, specificity >91%) in 3 studies but required confirmatory testing.

Can you have syphilis antibodies and not have syphilis? ›

If antibodies are found, it is called a reactive test. A reactive or positive test result does not always mean that you have syphilis. Other conditions can cause positive test results. These include injecting illegal drugs, recent vaccinations, endocarditis, and autoimmune diseases.

What is the difference between syphilis screen and RPR? ›

The syphilis total antibodies (IgG + IgM) screen is a new method relative to the RPR (rapid plasma reagin). The RPR detects non- treponemal antibodies (cardiolipin, cholesterol, and lecithin), whereas the new test detects IgG and IgM antibodies to T. pallidum proteins.

How long does syphilis screening take? ›

Results are usually available in 7 to 10 days. Normal: No syphilis antibodies are found. This is called a nonreactive or negative result.

What is one of the first signs of syphilis? ›

The first sign of syphilis is a small sore, called a chancre (SHANG-kur). The sore appears at the spot where the bacteria entered your body. While most people infected with syphilis develop only one chancre, some people develop several of them. The chancre usually develops about three weeks after exposure.

How long does it take to get a positive syphilis test? ›

Syphilis usually begins with a sore on the genitals called a chancre. Blood tests can detect the bacteria within 1–2 weeks after the chancre appears. Chancres are typically painless and usually develop within 3 weeks of exposure, so the total testing window is about 4 weeks.

What can cause false-positive syphilis? ›

Historically, false-reactive RPR test results have been observed in people with systemic infections unrelated to syphilis, such as tuberculosis, rickettsial diseases, and endocarditis. False-reactive RPR testing also has been previously observed following immunization (specifically following smallpox vaccine).

Does syphilis always show up on STD tests? ›

People who have suffered from a syphilis infection in the past could also have a false positive result due to syphilis antibodies lingering in the bloodstream. If a reliable testing method returns a negative result 90 days or later after exposure, it is considered a negative diagnosis.

How long can you have syphilis without knowing? ›

The average time between acquisition of syphilis and the start of the first symptom is 21 days. However, this can range from 10 to 90 days.

What does syphilis look like on a man? ›

A person with primary syphilis generally has a sore or sores at the original site of infection. These sores usually occur on or around the genitals, around the anus or in the rectum, or in or around the mouth. These sores are usually (but not always) firm, round, and painless.

How common are false syphilis tests? ›

We found a false positivity rate in total treponemal testing of 0.26%—0.1% in TPPA and 3% in RPR. Our population has a high number of prenatal screens and autoimmune diseases, both of which are more likely to have biological false positives in the RPR screen, a tendency we observed.

Can you pass syphilis without a sore? ›

Many people who have syphilis don't know it. You can have syphilis even if you don't notice any symptoms. The first symptom is a painless, round, and red sore that can appear anywhere you've had sex. You can pass syphilis to others without knowing it.

What is treponemal test positive in? ›

A reactive treponemal test most likely indicates infection by T pallidum but is not sufficient to determine disease activity and make treatment decisions (table 1). A reactive test can be seen in patients with a history of syphilis who has been treated.

What autoimmune disease causes syphilis? ›

The autoimmune response in natural and experimental syphilis, apparently triggered as a secondary reaction to T. pallidum infection, is represented by the production of various antibodies to self-antigens.

Can you still get hard with syphilis? ›

Currently, there's limited evidence that syphilis or human papillomavirus (HPV) have any impact on erections. However, one study has found that the herpes simplex virus (HSV) is associated with an increased risk of erectile dysfunction.

What disabilities does syphilis cause? ›

Untreated syphilis can lead to serious health problems, including blindness and damage to your brain, heart, eyes and nervous system.

How long does RPR stay positive? ›

The majority of patients who have reactive treponemal tests will have reactive tests for the remainder of their lives, regardless of adequate treatment or disease activity. However, 15%–25% of patients treated during the primary stage revert to being serologically nonreactive after 2–3 years (570).

What does a RPR of 1 4 mean? ›

The RPR antibody (a non-treponemal or reaginic antibody) titer of 1:4 may be associated with: 1) reinfection syphilis (immunity brought about by previous syphilis infection is incomplete)

Will RPR always be positive after treatment? ›

Following successful treatment, the RPR declines over time and may become nonreactive. However, the RPR may remain reactive at a low titer (generally <1:8), a condition referred to as the serofast state.

What are the signs of syphilis in a woman? ›

Painless, open sore(s) on the mouth, genitals, or anus. The sore(s) occurs at the location where syphilis entered the body. The sore(s) can be painless, making them difficult to find in the vagina or rectum. They usually last 3 to 6 weeks with or without treatment.

How often do you have to screen for syphilis? ›

At least once a year for syphilis, chlamydia, and gonorrhea. Those who have multiple or anonymous partners should be tested more frequently (e.g., every 3 to 6 months). At least once a year for HIV and may benefit from more frequent HIV testing (e.g., every 3 to 6 months).

What stage of syphilis is contagious? ›

Primary stage

This commonly occurs within 3 weeks of exposure but can range from 10 to 90 days. A person is highly contagious during the primary stage.

What are silent symptoms of syphilis? ›

These include:
  • A red rash that can appear anywhere on the body, but usually appears on the hands and / or feet.
  • Small skin growths.
  • White patches in the mouth.
  • Flu-like symptoms.
  • Swollen glands, (University of Michigan Health).

What does syphilis look like on the body? ›

The characteristic rash of secondary syphilis may appear as rough, red, or reddish brown spots both on the palms of the hands and the bottoms of the feet. However, rashes with a different appearance may occur on other parts of the body, sometimes resembling rashes caused by other diseases.

What do you feel if you have syphilis? ›

You may feel sick and have mild flu-like symptoms, like a slight fever, feeling tired, sore throat, swollen glands, headache, and muscle aches. You can also have sores in your mouth, vagina, or anus, and weight or hair loss.

Why am I still test positive for syphilis after treatment? ›

You can still test positive for treponemal antibodies after completing syphilis treatment. This means that treponemal antibody tests cannot distinguish between a current and past syphilis infection.

What is the traditional or reverse algorithm for diagnosis of syphilis? ›

Traditionally, the syphilis screening algorithm begins with a nontreponemal immunoassay, which is manually performed by a laboratory technologist. In contrast, the reverse algorithm begins with a treponemal immunoassay, which can be automated.

What is the best approach when testing for primary syphilis? ›

Primary syphilis is diagnosed by dark-field microscopy of a suspected lesion or by serologic testing (Table 2). Either technique can have a false-negative result early in the course of the disease. Thus, if clinical suspicion is high, treatment for syphilis should be initiated.

Which method is used for the detection of Treponema pallidum? ›

Direct detection methods for Treponema pallidum include dark-field microscopy (DFM), direct fluorescence antibody (DFA) testing, immunohistochemistry (IHC), and nucleic acid amplification tests (NAATs).

What does a 1 1 syphilis titer mean? ›

The titers refer to how many times you can dilute the sample and still get a positive result. So if you have lots of antibody you can water it down alot and it will still show up positive. For example: 1:1 is no dilution. 1:2 is diluted 50%.

What causes false positive RPR? ›

Historically, false-reactive RPR test results have been observed in people with systemic infections unrelated to syphilis, such as tuberculosis, rickettsial diseases, and endocarditis. False-reactive RPR testing also has been previously observed following immunization (specifically following smallpox vaccine).

What is the best way to diagnose secondary syphilis? ›

Secondary syphilis is diagnosed using positive darkfield examination and reactive treponemal or alternative non-treponemal tests.

Can you have syphilis for 20 years and not know it? ›

Without treatment you will still have syphilis for 20 years or more even though you will not have any signs or symptoms. People with latent syphilis may sometimes have symptoms (flare-ups) like skin rash, fever, a sore throat, swollen glands or feeling weak and tired.

What is the difference between RPR and Treponema pallidum? ›

Syphilis tests are available in two categories: treponemal tests (antibody tests to the organism itself, Treponema pallidum) and non-treponemal tests (such as RPR, which detects non-treponemal reagin antibodies; commonly seen with syphilis, but present in many other disease and non-disease states).

Is Treponema pallidum the same as syphilis? ›

Syphilis is a sexually transmitted disease (STD) caused by the bacterium Treponema pallidum. Syphilis can cause serious health effects without adequate treatment.

How accurate is Treponema pallidum test? ›

All immunoassays were 100% sensitive for secondary syphilis and 95.2–100% sensitive for early latent disease, but were less sensitive in late latent disease (86.8–98.5%).


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