IgA (Immunoglobulin A)

IgA (Immunoglobulin A) is the most abundant antibody found on the body's mucosal surfaces, including the respiratory tract, digestive tract, and genitourinary system. It plays a central role in neutralising pathogens and regulating immune responses at these barrier sites. This test measures the level of IgA in a simple blood sample and is used to investigate recurrent infections, chronic gastrointestinal or respiratory symptoms, and suspected immune deficiencies. It is also a key component in the assessment of autoimmune and inflammatory conditions, including coeliac disease, where IgA levels help determine whether further antibody testing is appropriate.

This test is suitable for adults and children who are experiencing unexplained recurrent infections, chronic diarrhoea, malabsorption, or symptoms suggestive of an immune disorder. It may also be requested as part of a broader autoimmune or immunoglobulin panel.

Biomarkers included

Immunoglobulins
- Immunoglobulin A (IgA)

Why it matters
IgA is a vital marker of mucosal immunity and immune competence. Abnormal levels can indicate selective IgA deficiency, chronic infection, inflammatory bowel disease, or other immune dysregulation. Identifying an IgA deficiency is particularly important before interpreting certain autoimmune tests, as it can lead to false-negative results. Measuring IgA gives clinicians a clearer picture of immune function and helps guide further investigation and management.