Neurosyphilis IgG Antibody Index with VDRL, Serum and Spinal Fluid
Order Code: pending
Fee Code: pending (CPT 86780)
Reference Laboratory: Mayo NSAIP
Mayo Clinic Laboratories will begin offering with Neurosyphilis IgG Antibody Index with VDRL, Serum and Spinal Fluid effective May 22, 2025. Testing begins with syphilis IgG screening of the spinal fluid (CSF) specimen. If the screen is negative, no additional testing will be performed.
If the CSF screen is reactive, the paired CSF and serum specimens will be used to establish the antibody index. To do this, the paired serum and CSF samples (collected within 24 hours of each other) are tested on the same run using quantitative assays to determine levels for the following analytes:
- Anti-Treponema pallidum IgG in CSF and serum
- Total IgG in CSF and serum
- Albumin in CSF and serum
These additional tests are necessary to normalize the level of anti-Treponema pallidum antibodies to total IgG
and albumin in the CSF and establish the antibody index ratio of anti-T. pallidum antibodies in CSF-to-serum.
This testing is performed at an additional charge (test ID NSAI). Samples that result as Syphilis Antibody Index negative do not undergo additional testing. Samples that result as Syphilis Antibody Index positive or equivocal will be reflexed for VDRL testing to establish a semi-quantitative titer at an additional charge (test ID VDSFT).
Collection Instructions: 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.
Collect 2.2 mL (minimum 1.5 mL) of CSF, place in a sterile vial, and refrigerate. The CSF must be collected within 24 hours of the serum specimen, preferably at the same time. 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. Label vial as spinal fluid or CSF.
Collect blood specimen in an SST (preferred) or red top tube. Centrifuge, aliquot 2.2 mL (minimum 1.5 mL) of serum into a plastic vial and refrigerate. Label vial as serum.
Band CSF and serum specimens together.
Test Limitations:
- A single negative result should not be used to exclude the diagnosis of neuroinvasive syphilis disease in a patient with appropriate exposure history and symptoms suggestive of infection.
- False-negative results may be acquired in patients tested soon after infection, prior to the development of a detectable level of antibodies in the spinal fluid.
- False-reactive results may occur in patients with Borrelia or Leptospira infections. Patient management decisions should not be made on a single reactive result.
- Antibody index can remain positive for a prolonged period of time after complete resolution of disease. Therefore, a positive result must be interpreted in light of current, presenting symptoms.
Test ID NSAIP includes the following test and reflex test components:
| Test ID | Description | CPT Code |
| NSCSF | Neurosyphilis IgG Screen, CSF | 86780 |
| NSSER | Neurosyphilis IgG, Serum | - |
| NSAI | Neurosyphilis IgG Antibody Index | 86780 x2, 82784 x2, 82040, 82042 |
| VDSFT | VDRL Titer, CSF | 86593 |