Immunoglobulins (Ig) can be measured in a blood analysis. They are defence proteins, also called antibodies. There are several types, named A, G, M. D, and E.
IgA, IgG and IgM are involved in the defence against infections. Their levels are low in some types of immunodeficiency, called humoral immunodeficiencies. On the other side, IgM can be abnormally raised as a compensatory mechanism in some immunodeficiencies with low IgG and IgA.
Specific levels of IgG or IgM are measured for the diagnosis and follow-up of many infectious diseases or to check response to anti infectious vaccines. Levels of IgG specific against some foods can be frequently found. They are not able to discriminate allergy from tolerance, and thus are not recommended. Sometimes specific IgG4 is measured to assess the efficacy of allergen immunotherapy or allergy vaccines.
Little is still know about IgD. High levels (hyper IgD) can be found in some cases of periodic fever syndrome.
No specific preparation, not even fasting, is needed if you are scheduled for an immunoglobulin measurement. Anyway, ask if other analytical results that require a preparation are requested at the same.
Angel Mazon MD, PhD