Syphilis Antibody, IgG, Serum
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
An aid in the diagnosis of active Treponema pallidum infection
Routine prenatal screening
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
If syphilis IgG is positive, no additional testing will be performed.
Multiplex Flow Immunoassay
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Syphilis IgG Ab, S
Syphilis G, Serum
Syphilis Serology (RPR)
Treponema pallidum (T. pallidum)
Syphilis Serology (RPR)
Treponema pallidum (T. pallidum)
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Preferred: Red top
Acceptable: Serum gel
Specimen Volume: 0.75 mL
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross reject
Mild OK; Gross reject
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Serum||Refrigerated (preferred)||14 days|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Syphilis is a disease caused by infection with the spirochete Treponema pallidum. The infection is systemic and the disease is characterized by periods of latency. These features, together with the fact that Treponema pallidum cannot be isolated in culture, mean that serologic techniques play a major role in the diagnosis and follow-up of treatment for syphilis.
Historically, the serologic testing algorithm for syphilis included an initial nontreponemal screening test, such as the rapid plasma reagin (RPR) or the venereal disease research laboratory (VDRL) tests. Because these tests measure the host's antibody response to nontreponemal antigens, they lack specificity. Therefore, a positive result by RPR or VDRL requires confirmation by a treponemal-specific test, such as the fluorescent treponemal antibody-absorbed (FTA-ABS) or microhemagglutination assay (MHA-TP). Although the FTA-ABS and MHA-TP are technically simple to perform, they are labor intensive and require subjective interpretation by testing personnel.
Recently, EIA and multiplex flow immunoassays (MFI) were introduced to assess serologic response to Treponema pallidum. The Bio-Rad BioPlex Syphilis IgG assay is an example of MFI technology, which utilizes specific, treponemal antigens coated on microspheres for the detection of IgG-class antibodies to Treponema pallidum. The BioPlex Syphilis IgG assay is highly sensitive and specific (see Supportive Data), and allows for an objective interpretation of results. Due to several factors including the low prevalence of syphilis in the United States, the increased specificity of treponemal assays, and the objective interpretation of MFI and EIA technology, initial serologic testing by a treponemal-specific assay (eg, EIA or MFI) is now commonly performed in clinical laboratories. Specimens testing positive by the treponemal-specific assay are then tested by RPR to provide supplementary serologic data, as well as to provide an indication of the patient's disease state and history of treatment.
During early primary syphilis, the first antibodies to appear are of the IgM-class, with IgG-class antibodies reaching significant titers later in the primary phase. As the disease progresses into the secondary phase, IgG-class antibodies to Treponema pallidum reach peak titers, and may persist indefinitely regardless of the disease state or prior therapy.
For prenatal syphilis screening, the IgG test is recommended. IgM testing should not be performed during routine pregnancy screening unless clinically indicated.
Treponema pallidum IgG antibodies persist indefinitely, regardless of the course of the disease. If treatment of an original Treponema pallidum infection was not monitored, a diagnosis of reinfection may actually represent either a resurgence of an inadequately treated earlier infection or persistent IgG antibodies from a resolved infection.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
A positive IgG treponemal test suggests infection withTreponema pallidum at some point in the past, but does not distinguish between treated and untreated infections. This is because treponemal tests (eg, EIA, multiplex flow immunoassay, or fluorescent treponemal antibody-absorbed) may remain reactive for life, even following adequate therapy. Therefore, the results of a nontreponemal assay, such as rapid plasma reagin, are needed to provide information on a patient's disease state and history of therapy.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test is not offered as a screening or confirmatory test for blood donor specimens.
Despite active syphilis, serologic tests may be negative in severely immunosuppressed patients such as those with AIDS.
In very early cases of primary syphilis, both IgM and IgG serologies may be negative.
In cases of old, successfully treated infection (>10 years earlier), both IgG and IgM serologies may be negative.
Results should be considered in the context of all available clinical and laboratory data.
To evaluate the accuracy of the BioPlex Syphilis IgG assay, 1,008 consecutive, unique serum specimens submitted for routine syphilis IgG testing by EIA were also tested on the BioPlex 2200. Specimens showing discrepant results were repeat tested by both methods, and also tested by Treponema pallidum-particle agglutination (TP-PA). The BioPlex 2200 Syphilis IgG assay correctly identified 77 (98.7%) of the 78 specimens that were positive by EIA. The EIA-positive, BioPlex-negative specimen was shown to be truly negative by TP-PA and repeat EIA. In addition, the BioPlex assay correctly identified 916 (98.5%) of the 930 specimens that were negative by EIA. Among the 14 BioPlex-positive, EIA-negative specimens, 8 were shown to be truly positive by TP-PA (see Table). The BioPlex Syphilis IgG assay demonstrated an adjusted sensitivity and specificity of 100% and 99.4%, respectively.
Table. Comparison of the Bio-Rad Syphilis IgG Assay and the Trep-Chek EIA Among Prospective Serum Specimens (n = 1,008).
a. 8/14 positive by Treponema pallidum-particle agglutination (TP-PA) upon follow-up testing
b. Negative by EIA upon repeat testing
Sensitivity: 77/78 = 98.7% (95% Confidence intervals: 92.4%, 99.9%)
Specificity: 916/930 = 98.5% (95% Confidence intervals: 97.5%, 99.1%)
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
Tramont EC: Treponema pallidum (Syphilis). In Principles and Practice of Infectious Diseases. 5th edition. Edited by GL Mandell, JE Bennet, R Dolin. New York, Churchill Livingstone, 2000, pp 2474-2491
Method Description Describes how the test is performed and provides a method-specific reference
The BioPlex Syphilis IgG is a multiplex flow immunoassay performed on the BioPlex 2200 System (Bio-Rad Laboratories, Hercules, CA). Three types of dyed beads are coated with recombinant proteins associated with Treponema pallidum (15kDa, 17kDa and 47kDa). An aliquot of patient sample, sample diluent, and bead reagent are combined in a reaction vessel, and the mixture is incubated at 37 degrees C. After a wash cycle, antihuman IgG antibody conjugated to phycoerythrin (PE) is added to the dyed beads, and this mixture is incubated at 37 degrees C. Excess conjugate is removed in another wash cycle and beads are resuspended in wash buffer. The bead mixture is then passed through a flow-based detector and identified according to the fluorescence emitted, which is specific to the internal dye composition of the microsphere. The amount of antibody bound to the capture antigen is then determined by measuring the fluorescence of the attached PE. Raw data is calculated in relative fluorescence intensity (RFI). (Package insert: BioPlex 2200 System Syphilis IgG [T.pallidum], Bio-Rad Laboratories Clinical Diagnostic Group, Hercules, CA)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Saturday; 9 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Same day/1 day
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|SYPGN||Syphilis IgG Ab, S||6561-5|