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HelpTest Code NSAI Neurosyphilis IgG, Antibody Index, Spinal Fluid
Specimen Required
Only orderable as part of a profile. For more information see NSAIP / Neurosyphilis IgG Antibody Index with VDRL, Serum and Spinal Fluid.
Both spinal fluid (CSF) and serum are required for this test. CSF and serum must be collected within a maximum of 24 hours of each other.
Specimen Type: Spinal fluid
Container/Tube: Sterile vial
Specimen Volume: 2.2 mL
Collection Instructions:
1. The spinal fluid (CSF) specimen must be collected within 24 hours of the serum specimen, preferably at the same time.
2. The CSF aliquot should be from the second, third, or fourth CSF vial collected during the lumbar puncture. Do not submit CSF from the first vial due to the possibility of blood contamination, which will cause specimen rejection.
3. Label vial as spinal fluid or CSF.
4. Band CSF specimen together with the serum sample.
Specimen Type: Serum
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Serum gel
Acceptable: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 2.2 mL
Collection Instructions:
1. Within 24 hours of collection of the spinal fluid specimen, a serum specimen must also be collected, preferably at the same time.
2. Centrifuge and aliquot serum into a plastic vial.
3. Label tube as serum.
4. Band serum specimen together with the CSF sample.
Secondary ID
621141Useful For
Aid in the diagnosis of neuroinvasive syphilis as part of a profile
Method Name
Only orderable as part of a profile. For more information see NSAIP / Neurosyphilis IgG Antibody Index with VDRL, Serum and Spinal Fluid.
Enzyme-Linked Immunosorbent Assay (ELISA)
Specimen Type
CSFSpecimen Minimum Volume
Spinal fluid: 1.5 mL; Serum: 1.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| CSF | Refrigerated (preferred) | 10 days |
| Frozen | 10 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Spinal fluid (CSF) contaminated with blood | Reject |
Reference Values
Only orderable as part of a profile. For more information see NSAIP / Neurosyphilis IgG Antibody Index with VDRL, Serum and Spinal Fluid.
Antibody Index: 0.6-1.2
Reference values apply to all ages.
Interpretation
Negative:
Results indicate lack of intrathecal antibody synthesis to syphilis (Treponema pallidum). This suggests the absence of neurosyphilis. The initial screen reactive result may be due to anti-syphilis antibodies present in the cerebrospinal fluid (CSF) due to increased permeability of the blood-brain barrier or transient introduction during lumbar puncture.
Equivocal:
Possible intrathecal antibody synthesis to syphilis (T pallidum) detected. Results should be correlated with exposure history and clinical presentation to establish a diagnosis of neurosyphilis. Sample has been reflexed for VDRL testing to establish a titer. False positive results may occur in patients with other spirochete infections (eg, Borrelia, Leptospira).
Positive:
Results indicate the presence of intrathecal antibody synthesis to syphilis (T pallidum), suggesting neurosyphilis. Results should be correlated with exposure history and clinical presentation to establish the diagnosis. Sample has been reflexed to VDRL testing to establish a titer. False positive results may occur in patients with other spirochete infections (eg, Borrelia, Leptospira).
Invalid:
Result is due to abnormally elevated total IgG levels in CSF. This may be due to passive diffusion through the blood-brain barrier or contamination of the CSF with blood during a traumatic lumbar puncture. Consider repeat testing if clinically indicated.
Method Description
The test kit contains microtiter strips with break-off reagent wells coated with purified recombinant Treponema pallidum antigens. In the first reaction step, diluted patient samples are incubated in the wells. In the case of positive samples, T pallidum-specific IgG antibodies will bind to the antigens. To detect the bound antibodies, a second incubation is carried out using an enzyme-labelled antihuman IgG (enzyme conjugate), followed by a third incubation using chromogen/substrate, which catalyzes a color reaction that is then measured for optical density (OD) using spectrophotometry. The obtained OD values of the paired patient serum and cerebrospinal fluid (CSF) samples are compared against a 4-level calibration curve to quantitatively determine the relative anti-T pallidum IgG antibody titers.(Unpublished Mayo method)
The quantitative test results obtained on paired serum and CSF specimens using the T pallidum IgG enzyme-linked immunosorbent assay are expressed as relative units (U/mL) and must be used along with the total IgG and albumin levels in the patient's paired serum and CSF samples to calculate the anti-T pallidum antibody index (AI), which determines the absence or presence of intrathecal anti-T pallidum IgG antibody synthesis. Total IgG and albumin testing on serum and CSF is performed using the Siemens BN II nephelometric testing system.(Instruction manual: Siemens Nephelometer II Operations. Siemens V 2.3, 2008; Addendum to the Instruction Manual 2.3, 08/2017)
To detect an infection of the central nervous system, it is necessary to differentiate between intrathecally produced antibodies and antibodies passed from blood into the CSF. The AI is the value of intrathecal pathogen-specific antibody production. This AI value represents the portion of pathogen-specific antibodies in total IgG of CSF and the portion of pathogen-specific antibodies in total IgG of serum. The patient's AI is calculated using the Reiber and Lange method.(Reiber H, Lange P. Quantification of virus-specific antibodies in cerebrospinal fluid and serum: sensitive and specific detection of antibody synthesis in brain. Clin Chem. 1991;37(7):1153-1160)
Day(s) Performed
Monday through Friday
Report Available
2 to 4 daysSpecimen Retention Time
2 weeksPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
82784 x 2
82040
86780 x 2
82042
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| NSAI | Neurosyphilis IgG, Ab Index | 105193-7 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| NSY3 | Neurosyphilis IgG Ab Index Value | 105193-7 |
| NSY4 | Neurosyphilis IgG Ab Index Interp | 69048-7 |