Immunoglobulins IgG, IgA and IgM

Category	Immunology and PRU
Reporting frequency	2 days

Additional information

Indication for test:

– Investigation of B cell malignancy eg myeloma, lymphoma

– Investigation of immune deficiency, particularly antibody deficiency

– Investigation of autoimmune liver disease or Sjogrens syndrome

– Monitoring of patients on immunosuppressive treatment, particularly anti-CD20 therapies, to evaluate infection risk.

Please note, in adults, immunoglobulin results are always checked by the lab by protein electrophoresis the first time tested in adults, but this is not repeated if the immunoglobulin pattern remains stable.

Interpretation of results if there is no paraprotein on protein electrophoresis

Raised IgG only	Can be seen in infection or inflammation, including some autoimmune disease.
Raised IgA only	Can be seen with inflammation affecting mucosal surfaces (airways, gut) and also sometimes with liver disease or some autoimmune disease.
Raised IgM only	This is typically seen with recent infection as part of the primary immune response. Less commonly, this can be seen in some autoimmune disease, such as primary biliary cholangitis.
Raised IgG and IgA	Pattern of persistent infection or inflammation.
Raised IgG and IgM	Pattern of persistent infection but can also be seen in some autoimmune disease.
Raised IgA and IgM	Pattern suggestive of recent infection affecting mucosal surfaces (airways, gut) or the liver.
Raised IgG, IgA and IgM	Pattern of severe infection or inflammation.
Low IgG only	This can be seen with some immunosuppressive treatments. The lab will test by protein electrophoresis to exclude the presence of a monoclonal protein the first time this pattern is seen.
Low IgA only	The IgA concentration can vary between individuals and a slightly low concentration is usually of no clinical consequence.  Undetectable or very low IgA (<0.07g/L) is seen in patients with IgA deficiency, which can be associated with an increased risk of autoimmunity, gluten sensitivity and rare risk of reactions with blood products.
Low IgM only	A slightly low IgM concentration is very common in older patients (>55 years old) without clinical consequence, but can also be caused by some immune suppression.
Two or three of IgG, IgA and IgM low	Pattern of immune suppression. The lab will test by protein electrophoresis to exclude the presence of a monoclonal protein the first time this pattern is seen.

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