Abstract
Patients who have recurrent infections require laboratory investigation for possible underlying immunodeficiency. We retrospectively evaluated the usefulness of two relevant assays (serum IgG subclass concentration and levels of IgG antigen-specific antibodies to a panel of relevant carbohydrate and protein antigens) in the management of patients referred to a regional clinical immunology service over a 3-year period. Of 97 patients for whom both assays were performed, five (5·2% ) had a low result for IgG subclasses but this did not influence the management of any patient; 51 patients (53%) had a low result for antigen-specific antibodies and this influenced management in 43 cases. We conclude that knowledge of the serum IgG subclass concentrations is of dubious relevance and this calls into question whether the assay should continue to be offered. This regional service has ceased to perform the assay routinely in such patients. Our findings require confirmation by a larger multicentre study that should assess the clinical outcome of any changes in practice.