Definition
- IgA makes up the majority of immunoglobulin in mucosal secretions, including nasal and pulmonary secretions, saliva and intestinal fluids, tears, and secretions of the genitourinary tract. IgA is important in preventing attachment or penetration of the body surfaces by microorganisms, and in protection against respiratory, GI, and GU infections. IgA cannot cross the placenta. It can be produced by infants, and their secretions tend to be typically low. IgA is the second most frequent type of monoclonal immunoglobulin identified in multiple myeloma.
- Normal ranges: see Table 16.41.
TABLE 16 " 41Normal Ranges for IgA by AgeView LargeTABLE 16 " 41Normal Ranges for IgA by Age Age Range (mg/dL) 0 " 30 d 1 " 7 1 mo 1 " 53 2 mo 3 " 47 3 mo 5 " 46 4 mo 4 " 72 5 mo 8 " 83 6 mo 8 " 67 7 " 8 mo 11 " 89 9 " 11 mo 16 " 83 1 y 14 " 105 2 y 14 " 122 3 y 22 " 157 4 y 25 " 152 5 " 7 y 33 " 200 8 " 9 y 45 " 234 10 " 17 y 68 " 378 ≥18 y 82 " 453
Use
- Detection or monitoring of monoclonal gammopathies and immune deficiencies
- Assist in the diagnosis of multiple myeloma
- Monitor therapy for multiple myeloma
- Evaluate patients suspected of IgA deficiency prior to transfusion
- Evaluate anaphylaxis associated with the transfusion of blood and blood products (anti-IgA antibodies may develop in patients with low levels of IgA, possibly resulting in anaphylaxis when donated blood is transfused)
Interpretation
Increased In
- Polyclonal:
- Cirrhosis of the liver
- Chronic infections
- Chronic inflammatory diseases
- Inflammatory bowel disease
- RA with high titers of RF
- SLE (some patients)
- Mixed connective tissue diseases
- Sarcoidosis (some patients)
- Wiskott-Aldrich syndrome
- Monoclonal:
- IgA myeloma (M component)
- Solitary plasmacytoma
- Alpha-heavy chain disease
- MGUS
- Lymphoma
- Chronic lymphocytic leukemia
Decreased In
- Normal persons (1:700)
- Hereditary telangiectasia (80% of patients)
- Type III dysgammaglobulinemia
- Malabsorption (some patients)
- SLE (occasionally)
- Cirrhosis of the liver (occasionally)
- Still disease (occasionally)
- Recurrent otitis media (occasionally)
- Non-IgA myeloma
- Waldenstr śm macroglobulinemia
- Acquired immunodeficiency
- Gastric carcinoma
Limitations
- Immunochemical methods do not distinguish between polyclonal and monoclonal levels. Serum protein electrophoresis and immunofixation need to be performed for quantification of M-proteins.