Neurosyphilis antibody index assay
Empowering confidence through state-of-the-art evaluation
Neurosyphilis is a form of syphilis infection that involves the brain and central nervous system. Without proper identification and care, neurosyphilis can lead to significant patient morbidity and possibly mortality. Accurate identification of neurosyphilis — which is caused by the bacterium Treponema pallidum— through laboratory testing is key to helping patients receive appropriate care and treatment.
The classic assay used for the diagnosis of neurosyphilis, known as the Venereal Diseases Research Laboratory Test, or VDRL test, is a non-treponemal (lipoidal) antibody test that is more than 80 years old and has limited specificity and sensitivity, which can lead to inaccurate and missed diagnoses.
Mayo Clinic Laboratories offers an alternative, innovative method to identify and confirm disease presence. The neurosyphilis antibody index assay — the only assay of its kind available in the U.S. — is a highly sensitive and specific approach that detects intrathecally synthesized antibodies specific to T. pallidum.
Neurosyphilis test menu
Neurosyphilis antibody index
Diagnosing neurosyphilis is challenging for several reasons, including ambiguity on the relevance of abnormal cerebrospinal fluid (CSF) results in patients who are seropositive for syphilis but neurologically asymptomatic.
Our antibody index assay, which is modeled after Mayo Clinic Laboratories’ first-in-class neuroinvasive Lyme disease antibody index, corrects for passive diffusion across an inflamed blood-brain barrier by measuring levels of anti-T. pallidum antibodies in serum and CSF, and normalizing those to total IgG and albumin in both specimen sources. Samples that result as syphilis antibody index positive or equivocal reflex to VDRL testing to establish a semi-quantitative titer.
Key testing
- NSAIP | Neurosyphilis IgG Antibody Index with VDRL, Serum and Spinal Fluid
- Facilitates diagnosis of neuroinvasive syphilis.
- Identifies whether the presence of IgG to T. pallidum in the CSF is due to true intrathecal antibody synthesis, which indicates neuroinvasive syphilis.
- Provides higher specificity and sensitivity than the classic VDRL assay for neurosyphilis.
- Results available in 2–4 days.
Additional information
- Testing begins with syphilis IgG screening of the 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 through quantitative testing to determine levels for:
- Anti-Treponema pallidum IgG in CSF and serum
- Total IgG in CSF and serum
- Albumin in CSF and serum
- These additional tests are needed to normalize the level of anti-T. 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 using the Reiber formula. This testing is performed at an additional charge.
Highlights
Breaking away from an 80-year-old testing approach used to identify neurosyphilis infections, Mayo Clinic Laboratories has introduced a new, highly sensitive and specific method to confirm disease presence. The innovative test – the only one of its kind available in the U.S. – is IgG antibody index that detects antibodies specific to the disease-causing agent Treponema pallidum.
VDRL assay
In patients with a history of syphilis infection, the VDRL test can be used to diagnose neurosyphilis. This test is a nontreponemal serologic assay that uses cerebrospinal fluid (CSF) to detect IgG and IgM antibodies directed against the lipoidal antigens released from cells damaged by the infection.
Key testing
- VDSF | VDRL, Spinal Fluid
- Aids in diagnosing neurosyphilis.
- NOTE: Positive tests will automatically reflex to VDRL titer at an additional cost.