Overview: Immunoglobulin G Subclass 4 TestIntroduction: The Immunoglobulin G Subclass 4 Test measures IgG subclass 4 to diagnose immune deficiencies, causing recurrent infections. Aligned with 2023 AAAAI guidelines, it uses immunoassays for high accuracy, supporting immune screening. This test is critical for guiding diagnosis, treatment planning, and improving outcomes in immunology for patients with suspected immune deficiencies.
Other Names: IgG4 Assay, IgG Subclass 4 Test.
FDA Status: Laboratory-developed test (LDT), meeting immunology standards for diagnostic accuracy.
Historical Milestone: IgG subclass testing began in the 1980s with immune deficiency research. Immunoassay-based methods improved in the 2000s, enhancing diagnostic precision.
Purpose: Measures IgG subclass 4 to diagnose immune deficiencies, guides treatment, and evaluates patients with recurrent infections.
Test Parameters: 1. IgG Subclass 4
Pretest Condition: No fasting required. Collect serum, plasma, or saliva at any time. Report history of recurrent infections or immune deficiencies.
Specimen: 2-5 mL serum (SST), 2-4 mL plasma (EDTA), or 1-2 mL saliva (sterile container). Transport in a biohazard bag.
Sample Stability at Room Temperature: 8 hours
Sample Stability at Refrigeration: 7 days
Sample Stability at Frozen: 6 months
Medical History: Document recurrent infections, sinusitis, or family history of immune deficiencies. Include current medications, especially immunoglobulins.
Consent: Written consent required, detailing the tests purpose, immune deficiency implications, and potential need for immunoglobulin therapy.
Procedural Considerations: Uses immunoassays to measure IgG4 levels. Results are available in 1-2 days, supporting rapid clinical decisions. Performed in laboratories, often for immune assessment.
Factors Affecting Result Accuracy: Improper sample handling or contamination can affect results. Recent infections or immunoglobulin therapy may influence levels.
Clinical Significance: Low IgG4 suggests immune deficiency, guiding immunoglobulin therapy. Elevated IgG4 may indicate IgG4-related disease, requiring further testing.
Specialist Consultation: Consult an immunologist for result interpretation and treatment planning.
Additional Supporting Tests: Total IgG, IgA, IgM, or lymphocyte subset analysis to assess immune function.
Test Limitations: Not specific to one immune deficiency; clinical correlation is needed. IgG4 levels vary with age or infections.
References: AAAAI Immune Deficiency Guidelines, 2023; Journal of Allergy and Clinical Immunology, Bonilla FA, 2022.
