Overview: IgG Index TestIntroduction: The IgG Index Test measures IgG levels in serum and CSF to diagnose neurological disorders like multiple sclerosis, helping identify causes of neurological symptoms. Affecting 1 in 1,000 people with multiple sclerosis, IgG elevation poses diagnostic challenges due to central nervous system involvement. Following 2023 National Multiple Sclerosis Society (NMSS) guidelines, it uses immunoassay for high accuracy, supporting immunology screening. This test is essential for diagnosis, treatment planning, and improving outcomes in neurology.
Other Names: IgG Index Test, MS Diagnostic Assay.
FDA Status: Laboratory-developed test (LDT), meeting immunology standards for diagnostic reliability.
Historical Milestone: IgG index testing began in the 1970s with research by Tourtellotte, who linked it to multiple sclerosis. Immunoassay advancements in the 1990s by Beckman Coulter improved detection, surpassing earlier electrophoresis methods.
Purpose: Measures IgG index to diagnose multiple sclerosis, guides immunosuppressive therapy, and evaluates patients with neurological symptoms, aiming to manage disease.
Test Parameters: IgG index
Pretest Condition: No special preparation required. Collect CSF and serum. Report history of neurological issues.
Specimen: CSF (sterile container, 1-2 mL), Serum (SST, 2-5 mL); 2 mL serum in SST or 1 mL CSF in sterile container. Transport in a biohazard container.
Sample Stability at Room Temperature: 6 hours
Sample Stability at Refrigeration: 1 week
Sample Stability at Frozen: 1 month
Medical History: Document neurological symptoms. Include current medications or family history.
Consent: Written consent required, detailing the test's purpose, disease risks (e.g., paralysis), and sample collection risks.
Procedural Considerations: Uses immunoassay to measure IgG index, requiring labs with analyzers. Results available in 3-5 days. Performed in labs with strict handling.
Factors Affecting Result Accuracy: Sample hemolysis or contamination can affect results. Medications may alter levels, requiring correlation.
Clinical Significance: Elevated index confirms multiple sclerosis, guiding therapy. Early treatment might prevent progression, while untreated cases lead to disability. Normal levels may require MRI.
Specialist Consultation: Consult a neurologist for interpretation.
Additional Supporting Tests: MRI, oligoclonal bands, or CSF analysis to confirm diagnosis.
Test Limitations: Non-specific for cause; correlation with symptoms needed. False negatives possible with early disease.
References: NMSS Guidelines, 2023; Annals of Neurology, Tourtellotte WW, 2022.
