RT Journal Article SR Electronic T1 How to use immunoglobulin levels in investigating immune deficiencies JF Archives of disease in childhood - Education & practice edition JO Arch Dis Child Educ Pract Ed FD BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health SP 129 OP 135 DO 10.1136/archdischild-2015-309060 VO 101 IS 3 A1 Fani Ladomenou A1 Bobby Gaspar YR 2016 UL http://ep.bmj.com/content/101/3/129.abstract AB Children are often referred to immunologists for the evaluation of reduced serum immunoglobulins. Knowledge of the immunoglobulin levels in healthy children of different ages is necessary when estimating immunological deficiency states of various kinds. After the measurement of the serum levels of the three major isotypes, examination of the capacity of the child to form antibodies to several antigens is a reasonable next step in the evaluation. We can rely on vaccine responses to make the distinction between significant primary immunodeficiency diseases and transiently low immunoglobulin levels. On the other hand, normal values of IgM, IgG and IgA are not always enough to exclude a more serious condition. Regardless of immunoglobulin concentrations, if a child's history indicates that further evaluation is warranted, a complete humoral immunity study should be carried out, including IgG subclasses, specific antibody responses and identification of B lymphocyte populations.