|Downtime form:||A-1a Doctor/Provider Orders - Pathology Core and Specialty Care Nursery|
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. The new approach to syphilis is termed 'reverse algorithm' in that RPR is not done as first test (traditional algorithm) but as the confirmation (i.e., reverse of the traditional algorithm). A negative syphilis total antibodies means that past and present syphilis infection is unlikely. A positive syphilis total antibodies reflexes automatically to RPR. If there is discrepancy between syphilis total antibodies and RPR, TPPA (T. pallidum particle agglutination) is additionally performed. A negative syphilis total antibodies means that past or present syphilis infection is unlikely. A positive syphilis total antibodies can indicate a past or present infection. Specimens showing positive syphilis total antibodies will be reflexed automatically to RPR. If there is discrepancy between syphilis IgG and RPR, TPPA is additionally performed. For patients who have been treated for syphilis, RPR titers should be followed (orderable as Syphilis Treatment Follow-up (RPR with Titer) in Epic). Successful treatment is generally indicated by a 4-fold or more reduction in RPR titer (e.g., 1:32 to 1:8). As mentioned above, positive syphilis total antibodies can occur with past or present infection. The interpretation is as follows using CDC guidelines: Syphilis Total Antibodies RPR TPPA Interpretation Negative (Not done) (Not done) Syphilis infection unlikely Positive Positive (Not done) Syphilis - recent infection likely Positive Negative Positive Syphilis - past or present infection Positive Negative Negative Infection unlikely - false positive syphilis total antibodies. There are several advantages of the reverse algorithm: •Rapid turnaround time for syphilis total antibodies •Avoids the false positives seen with RPR in autoimmune disease (e.g., lupus), infectious mononucleosis, viral pneumonia, and non-syphilis treponemal diseases (e.g., yaws) •Detects early primary and latent infection that may be missed with traditional RPR screening. Some key points to remember with the reverse algorithm: •Syphilis total antibodies can persist for many years. A positive result does not necessarily indicate active disease. In patients with positive syphilis total antibodies, the RPR provides information on active versus past infection. •For assessing treatment efficacy in patients who have been treated for syphilis, "Syphilis Treatment Follow-up (RPR with Titer)" should be ordered. Successful treatment is generally indicated by a 4-fold reduction in RPR titer (e.g., 1:32 to 1:8). •The syphilis total antibodies can have false positives. These will be indicated by negative RPR and TPPA confirmation. Given the generally low prevalence of syphilis in Iowa, false positives will be a significant fraction of positive screening test results regardless of testing method used. •Iowa Department of Public Health will investigate positive syphilis total antibodies results only after confirmatory testing results are available. The full set of results guides investigation and follow-up.
Positive syphilis total antibodies results are reflex automatically to RPR. If syphilis total antibodies and RPR results are discrepant, TPPA is additionally performed. For those samples that reflex to RPR testing, RPR assay interference resulting in false positive results may occur with cross-reacting antibodies from patients diagnosed with systemic lupus erythematosus, malaria, autoimmune disease, viral pneumonia, and people who have been recently vaccinated (including vaccines for SARS-CoV-2). RPR results should be interpreted in conjunction with patient history, risk factors, and other syphilis testing.
This assay may be significantly impacted by high-dose biotin (>5 mg dose) taken within previous 12 hours. High concentrations of biotin may lead to falsely decreased results. These concentrations may be found in patients taking over-the-counter supplements with biotin content much higher than nutritional requirements for biotin. Specimens should not be collected until at least 12 hours after the last dose.
86592 (RPR - if performed as reflex)
86593 (RPR titer - if performed as reflex)
86780 (TPPA - if performed as reflex)