Analysis of immunoglobulin isotype levels in acute pneumococcal bacteremia and in convalescence

In 48 patients with a history of a pneumococcal bacteremia, serum taken during the acute phase of the infection was analyzed for IgG and IgG subclasses. Once the patients were free of infection, a serum sample was analyzed for IgG, IgG subclasses, IgA and IgM. In an additional 20 patients, it was only possible to analyze serum from the infection-free phase. Seventeen of 48 (35%) patients had reduced levels of total IgG or of one or more of the IgG subclasses during acute disease. Of the 48 patients in whom both acute phase and infection-free phase serum were analyzed, values of IgG (p < 0.001), IgG1 (p < 0.001), IgG2 (p < 0.001), IgG3 (p < 0.01) and IgG4 (p < 0.01) were decreased during the acute infection. During the infection-free phase, 12 of 68 (18%) patients had a recognizable immunodeficiency, including two patients with common variable immunodeficiency. Routine screening for immunoglobulins during the infection-free period could result in the discovery of previously unrecognized immunoglobulin deficiencies in patients with a history of bacteremic pneumococcal infection.