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Test Code LAB4202 SYPHILIS IgG ANTIBODY W/REFLEX TO RPR SCREEN

Important Note

Reactive or equivocal results are reflexed to a Rapid Plasma Reagin (RPR) screen. Reactive RPR results will reflex further to a RPR titer.  Non-reactive RPR results will reflex to a second treponemal Syphilis TP-PA antibody test. This test is performed at Mayo Clinic.

Specimen Type

Preferred Sample: Serum (SST, Gold, Corvac, Tiger, Red Top Tube)

Alternative Sample: EDTA Plasma (Lavender Top Tube)

 

Specimen Volume

1 mL

Minimum Volume

0.5 mL

Turnaround Time

3 Days

Test Schedule

Monday, Wednesday, Friday

Sample Stability

Serum: 5 days at 2-8°C; 1 year at -15 to -20oC Plasma: 2 days at 2-8oC

Method

CAPTIATM  ELISA

Reference Ranges

Negative

Analyte Non Reactive Equivocal Reactive
SYPHILIS, IgG <0.9 >0.9 to <1.1 > 1.1

Synonyms

syphilisT, Treponema pallidum

CPT Codes

86780

Specimen Rejection

Do not use lipemic, hemolyzed, or turbid specimens.

Interpretation

Treponemal Result CAPTIA™ Syphilis - IgG

Non-Treponemal Result (NT)

Report/interpretation for all except neonates or infants.2

Negative (nonreactive) 

Antibody Index ≤ 0.9

Nonreactive

No serological evidence of infection with T. Pallidum

(incubating or early primary syphilis cannot be excluded).

Negative (nonreactive)

Antibody Index ≤ 0.9

Reactive

Current infection unlikely, probability of biological false positive secondary to other medical conditions (febrile diseases, immunizations, IV DU, autoimmune diseases, etc.). Recommend repeat testing (non-treponemal and treponemal by other test method). 

Positive (reactive) Antibody Index ≥ 1.1

Nonreactive

Probably past infection or potential cross-reactivity with other spirochetes/related antigens; additional testing appropriate to clinical findings/history;1 possibility of false negative non-treponemal (NT) due to prozone and late syphilis or neurosyphilis.

Positive (reactive) Antibody Index ≥ 1.1

Reactive

Presumptive evidence of current infection (or inadequately treated infection, persistent infection, reinfection, or biological false positive if prior history); additional testing consistent with clinical assessment.1

Negative (nonreactive)

Antibody Index ≤ 0.9

Not done

Current or past infection unlikely; cannot exclude incubating or early syphilis.

1 Quantitative non-treponemal testing; clinical history; repeated (sequential) serological testing for changes in titer. 2 HIV-infected individuals may have delayed seroreactivity or negative serology.

Limitations

  • Results from CAPTIA™ Syphilis-G should be considered in the context of all available clinical and laboratory data.
  • A CAPTIA™ Syphilis-G non-reactive result does not preclude the possibility of:
        (a) a very recent infection (within the last 2-3 weeks) with T.pallidum. (b) an old, successfully cured infection with T. pallidum (for example >10 years previous).
  • CAPTIA™ Syphilis-G may be reactive with sera from patients with Yaws (T. pallidum subspecies pertenue) or Pinta (T. carateum).
  • Detection of treponemal antibodies may indicate recent, past, or successfully treated syphilis infections, therefore, the test cannot be used to differentiate between active and cured cases.
  • When performing clinical lab assays, any sera giving reactive or equivocal results must be supplemented with a quantitative non-treponemal test (such as RPR and VDRL) to distinguish active disease and assist in ruling out false positives. The CAPTIA™ Syphilis-G is a treponemal assay, therefore patients with previously treated syphilis will be positive on the assay. 
  • The use of CAPTIA™ Syphilis-G as an initial screening test for blood donors may result in higher numbers of reactive donors who may not be currently infected compared to screening donors with standard, non-treponemal assays. It is recommended that CAPTIA™ Syphilis-G repeat reactive specimens be tested by methods capable of indicating the current disease status of the donor e.g. RPR and VDRL tests.
  • AIDS patients with impaired immunity and who are co-infected with syphilis may react falsely nonreactive in treponemal and non-treponemal tests.
  • Reactive treponemal IgG antibody test results usually remain reactive for a lifetime; therefore, antibody indices cannot not be used to determine response to therapy.