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Test 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.


Useful 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)

Reporting Name

Neurosyphilis IgG, Ab Index

Specimen Type

CSF

Specimen 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

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.

Clinical Reference

1. Alberto C, Deffert C, Lambeng N, et al. Intrathecal Synthesis Index of Specific Anti-Treponema IgG: A New Tool for the Diagnosis of Syphilis. Microbiol Spectr. 2022;10(1):e01477-21

2. Papp JR, Park IU, Fakile Y, Pereira L, Pillay A, Blan GA. CDC Laboratory Recommendations for Syphilis Testing, United States. MMWR Recomm Rep. 2024;73(1):1-32

3. Klein M, Angstwurm K, Esser S, et al. German guidelines on the diagnosis and treatment of neurosyphilis. Neuro Res Pract. 2020;2(33):1-9

4. Wu S, Ye F, Wang Y, Li D. Neurosyphilis: insights into its pathogenesis, susceptibility, diagnosis, treatment and prevention. Front Neurol. 2024;14:1340321

5. 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 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

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