From the Guidelines
Elevated or low Immunoglobulin A (IgA) levels should be interpreted with caution, considering the patient's clinical symptoms and other laboratory findings, as they can indicate various medical conditions, including chronic inflammation, infections, autoimmune disorders, or primary immunodeficiencies, such as selective IgA deficiency, which can increase susceptibility to infections and autoimmune diseases 1.
Interpretation of IgA Levels
Elevated IgA levels typically indicate chronic inflammation, infections, autoimmune disorders, or certain cancers, while low IgA levels suggest selective IgA deficiency or other conditions such as protein-losing disorders or congenital defects.
- Elevated IgA levels (above 400 mg/dL in adults) may indicate:
- Chronic inflammation
- Infections
- Autoimmune disorders like rheumatoid arthritis or lupus
- Liver diseases such as alcoholic cirrhosis
- Certain cancers including multiple myeloma and IgA monoclonal gammopathy
- Low IgA levels (below 70 mg/dL in adults) may suggest:
- Selective IgA deficiency, the most common primary immunodeficiency
- Protein-losing conditions
- Certain medications
- Congenital disorders
Selective IgA Deficiency
Selective IgA deficiency is often asymptomatic but can increase susceptibility to:
- Respiratory infections
- Gastrointestinal infections
- Urinary tract infections
- Allergies
- Autoimmune disorders Patients with severe IgA deficiency (less than 7 mg/dL) should be monitored over time for the occurrence of complications, such as respiratory and gastrointestinal tract infections, atopy, autoimmune diseases, celiac disease, and malignancy, and should be cautious with blood products due to potential anaphylactic reactions 1.
Clinical Considerations
It is essential to interpret IgA levels in context with clinical symptoms and other laboratory findings, as values can vary with age, and some healthy individuals may have naturally low levels without clinical significance.
- Patients with elevated IgA levels often require further testing to determine the underlying cause.
- The presence of elevated IgG levels, especially in the absence of cirrhosis, can be a distinctive feature of autoimmune hepatitis, and a selectively elevated IgG in the absence of IgA and IgM elevation is particularly suggestive of this condition 1.
From the Research
Interpretation of IgA Lab Levels
Elevated or low Immunoglobulin A (IgA) lab levels can have various clinical implications.
- Low IgA levels, also known as selective IgA deficiency (SIgAD), is the most common primary immunodeficiency, which can increase the risk of sinopulmonary infections, gastrointestinal infections, and autoimmune diseases such as systemic lupus erythematosus, hyper- and hypo-thyroidism, Type 1 diabetes, and celiac disease 2, 3.
- Patients with SIgAD may also be at risk of developing anti-IgA IgE antibodies, which can result in anaphylaxis if blood products with IgA are administered 2.
- Elevated IgA levels can be associated with certain autoimmune diseases, such as rheumatoid arthritis, and may also be influenced by factors such as age, sex, and smoking habits 4.
- Secondary IgA deficiency can be caused by medications, infections, or malignancies, and may require different treatment approaches than primary IgA deficiency 2, 5.
Clinical Implications
The clinical implications of IgA deficiency can vary depending on the individual and the underlying cause of the deficiency.
- Some patients with IgA deficiency may not experience any significant clinical symptoms, while others may be at increased risk of infections and autoimmune diseases 3, 6.
- The diagnosis of IgA deficiency is typically based on serum IgA levels, although most IgA is secreted at mucosal surfaces and may not be detectable through blood tests 2.
- Treatment for IgA deficiency may involve prophylactic antibiotics, supplemental IgG infusions, and monitoring for potential complications such as anaphylaxis and autoimmune diseases 2, 5.
Associations with Autoimmune Diseases
IgA deficiency has been associated with various autoimmune diseases, including: