Syphilis Total Antibodies with Reflex Confirmation
Label Mnemonic: SYPHT
Epic code: LAB8631
Downtime form: A-1a Doctor/Provider Orders - Pathology Core and Specialty Care Nursery
Chemistry
6240 RCP
356-3527
Specimen(s):
Serum
Collection Medium:
Red top tube 5 mL (Clot Activator)
Minimum:
5 mL serum from red top tube
Testing Schedule:
24 hrs/day, 7 days a week, including holidays.
Turn Around Time:
2 hours (upon receipt in laboratory)
Reference Range:
Negative
Interpretive Data:
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.
Comments:
New assay (switch from syphilis IgG to syphilis total antibodies) introduced April 3, 2018.

Positive syphilis total antibodies results are reflex automatically to RPR. If syphilis total antibodies and RPR results are discrepant, TPPA is additionally performed.

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.
Test Limitations:
The assay is unaffected by icterus < 66 mg/dL, hemolysis (Hb < 500 mg/dL), or lipemia < 2000 mg/dL).
Methodology:
Multiplex flow immunoassay
CPT Code:
86780 (Syphilis total antibodies)
86592 (RPR - if performed as reflex)
86593 (RPR titer - if performed as reflex)
86780 (TPPA - if performed as reflex)