Diagnostic Use
Immunoglobulin requests are routinely tested for IgG, IgA and IgM only. Serial monitoring should ideally be done through the same laboratory as levels may not be directly comparable due to variation in the assays used.
Interpretation
| Reduced IgG |
| Low IgG may be due to primary immunodeficiency or secondary causes (e.g. multiple myeloma, B cell depleting agents such as rituximab). |
| Adult IgG < 1g/ L |
Severe hypogammaglobulinemia, at risk of life threatening or severe infection. Please refer to Clinical Immunology for further advice. |
| Adult IgG 1 – 3g/ L |
If no known cause, investigate for secondary causes and consider a Clinical Immunology referral if no cause is identified. |
| Adult IgG 3- 5g/ L |
If no cause is identified or there is recurrent, particularly sinopulmonary, infections or other features of an immunodeficiency consider referral to Clinical Immunology. |
| Paediatrics (<12 years)
IgG below lower limit for age |
If IgG levels are reduced and there is no known cause, consider a paediatric immunology referral. |
| Reduced or undetectable IgA |
| Selective IgA deficiency is common, seen in approximately 1:400 people, it is often asymptomatic. Associated with coeliac disease, inflammatory bowel disease, transfusion reactions (when IgA absent) and rarely infection.
Low IgA seen in conjunction with low IgG or IgM: consider primary or secondary immunodeficiency.
Paediatrics: IgA levels may be undetectable < 7 months. IgA deficiency cannot be reliably diagnosed <5 years old. |
| Elevated IgA, IgM or IgG |
| May be polyclonal (e.g. infection, autoimmune or liver disease) or monoclonal.
Serum protein electrophoresis should be considered, particularly in patients with evidence of immunoparesis to at least one other immunoglobulin isotype or where IgG >25g/L, IgA>10g/L or IgM >10g/L. |
Reference Intervals
| IgG |
(g/L) |
| Newborn to <2 weeks |
3.0 – 13.7 |
| 2 weeks to <6 weeks |
1.2 – 6.0 |
| 6 weeks to <6 months |
1.2 – 7.0 |
| 6 months to <12 months |
3.0 – 10.5 |
| ≥1 year to <4 years |
3.0 – 11.2 |
| 4 years to <10 years |
5.0 – 13.3 |
| 10 years to <19 years |
6.0 – 15.0 |
| 19 years to <70 years |
7.0 – 16.0 |
| ≥70 years |
6.0 – 15.0 |
| IgA |
(g/L) |
| Newborn to <1 year |
< 0.4 |
| ≥1 year to <3 years |
< 1.1 |
| 3 years to <6 years |
< 1.7 |
| 6 years to <14 years |
0.3 – 2.4 |
| 14 years to <19 years |
0.4 – 3.1 |
| 19 years to <70 years |
0.8 – 4.0 |
| ≥70 years |
0.8 – 4.0 |
| IgM |
(g/L) |
| Newborn to <2 weeks |
<0.5 |
| 2 weeks to <13 weeks |
0.1 – 0.7 |
| 13 weeks to <1 year |
0.1 – 0.9 |
| 1 year to <19 years |
0.4 – 1.8 |
| 19 years to <70 years |
0.4 – 2.5 |
| ≥70 years |
0.4 – 2.4 |
Test Method
Principle: Immunoturbidimetric Assay
Reagents: Siemens Atellica CH Immunoglobulin A, G and M.
Analyser: Siemens Atellica CH
Uncertainty of Measurement
This information is available upon request.