From the Guidelines
Follow-up testing is necessary to resolve the discordant results and determine the presence of a past or current syphilis infection, as the negative RPR does not rule out past treated infection or very early or late untreated infection. The patient's Treponema antibody positive result, combined with a negative RPR screen and negative Treponema pallidum ab, suggests the need for further evaluation to guide management decisions, as stated in the 2018 update by the Infectious Diseases Society of America and the American Society for Microbiology 1.
Key Considerations
- The negative RPR (non-treponemal test) indicates there is likely no active infection, but doesn't rule out past treated infection or very early or late untreated infection.
- The positive Treponema antibody test may indicate past or current infection, but requires confirmation with another treponemal-specific test, such as fluorescent treponemal antibody–absorbed, as recommended by the guidelines 1.
- Repeating both treponemal tests (Treponema antibody and Treponema pallidum antibody) in 2-4 weeks and consulting with an infectious disease specialist if discordance persists is a reasonable approach.
Clinical Implications
- Syphilis can have serious long-term health consequences if missed, making follow-up particularly important even with the negative RPR.
- Various factors can cause false results, including technical issues, cross-reactivity with other conditions, or timing of testing relative to infection, highlighting the need for careful interpretation of test results and consideration of clinical context.
- The presence of risk factors for syphilis or symptoms would make follow-up particularly important, as it may indicate a higher likelihood of infection or complications.
From the Research
Interpretation of Test Results
- The patient's test results show a positive Treponema antibody, a negative RPR screen, and a negative Treponema pallidum ab.
- According to the study 2, the TPHA test should be used in addition to the FTA-abs test as a confirmatory test, suggesting that a negative TPHA result does not necessarily rule out syphilis infection.
- The study 3 found that automated TPLA results had a high concordance with recomBlot Treponemal IgG/IgM results, but there were discrepancies between TPLA and TPHA results, indicating that further testing may be necessary to confirm diagnosis.
Need for Follow-up
- The study 4 recommends further analysis by Treponema pallidum particle agglutination to confirm diagnostic results due to the possibility of false-positive results using chemiluminescent microparticle immunoassay for routine screening of syphilis.
- The study 5 found that isolated reactive CIA specimens may represent true T. pallidum infection and may be found after seroreversion of traditional treponemal assays, suggesting that follow-up testing may be necessary to determine the presence of syphilis infection.
- The study 6 found that serum IgA can be a sensitive and specific marker of syphilis, and its detection could be used as a screening assay for active infection, which may be useful in follow-up testing.
Clinical Implications
- The patient's test results and medical history should be reviewed to determine the need for further testing or treatment.
- The studies suggest that a combination of tests, including non-treponemal and treponemal tests, may be necessary to confirm the diagnosis of syphilis.
- Follow-up testing may be necessary to determine the presence of syphilis infection, especially in high-prevalence populations or in patients with a history of syphilis infection 5.