From the Research
The normal standard reference range for Immunoglobulin G4 (IgG4) in an adult white male is typically between 3 to 201 mg/dL (0.03 to 2.01 g/L). This range may vary slightly depending on the laboratory and testing method used, as noted in the study by 1. IgG4 is one of the four subclasses of Immunoglobulin G, making up approximately 3-6% of total IgG in healthy adults.
Key Points to Consider
- It's essential to interpret IgG4 levels in the clinical context, as elevated levels (>135 mg/dL) may suggest IgG4-related disease, a group of immune-mediated conditions characterized by tissue infiltration with IgG4-positive plasma cells and fibrosis, as discussed in 2 and 3.
- However, some individuals may have elevated IgG4 levels without disease manifestations, while others with IgG4-related disease might have normal levels, highlighting the importance of considering clinical presentation, imaging findings, and histopathological examination when appropriate, as mentioned in 4.
- The optimal cutoff value of serum IgG4 for the diagnosis of IgG4-RD was found to be 248 mg/dL, with a sensitivity and specificity of 77.6% and 92.8%, respectively, according to the study by 5.
Clinical Implications
- Diagnosis should not be based solely on serum IgG4 concentration but should include a comprehensive evaluation of the patient's clinical presentation, imaging findings, and histopathological examination when appropriate.
- The reference range for IgG4 may vary depending on the laboratory and testing method used, and it's crucial to consider these factors when interpreting test results, as noted in 1.