Specific antibody deficiency with normal immunoglobulin concentration in children with recurrent respiratory infections

BackgroundResponse to polysaccharide antigens is a test to evaluate the immunological competence of children with recurrent respiratory infections (RRI) of unknown cause and no other immune system abnormality. In order to detect specific antibody deficiency (SAD), a group of children with RRI without other immunodeficiency were prospectively studied.MethodsWe included 20 children (12 male), age range 3–14 years, with six or more annual episodes of respiratory infections (RI); one or more monthly episodes of RI during the winter months; or three or more annual episodes of lower RI. The children were immunised with 23-valent polysaccharide anti-pneumococcal vaccine, and ELISA was used to measure anti-polysaccharide IgG antibody levels for 10 pneumococcal serotypes at baseline (T0), and 45 days (T1) and one year post-immunisation (T2). Post-immunisation response above 1.3 μg/ml for more than 50% of the serotypes was considered normal for children 2–5 years, and for more than 70% of the serotypes in children older than 5 years.ResultsAt T1 19/20 children showed a normal response for their age, and only one patient showed a deficient response, suggestive of classic moderate SAD. At T2, 8/20 patients showed deficient responses, suggestive of impaired persistence of specific antibodies. There was a noteworthy association between deficient response and asthma and allergic rhinitis.ConclusionsWe propose first ruling out local or systemic causes, then performing serum immunoglobulin IgM, IgG, IgA, IgE and IgG subclass levels, and finally measuring response to polysaccharide pneumococcal antigens for detection of SAD.