In a 4-year old boy who has history of pyogenic infections by bacteria with polysaccharide-rich capsules, which of the following investigations should he done?

Ans. d. IgA and IgG2 deficiency Recurrent episodes of pyogenic infections by capsulated organisms are most commonly observed in patients with selective IgA deficiency and decreased IgA or IgG subclass levels (especially IgG2). "Specific Antibody Deficiency (SAD) patients generally present with recurrent upper and/or lower respiratory infections due to an encapsulated organisms (Streptococcus pneumonia, Haemophilus influenza, Branhamella catarrhalis, or Staphylococcus aureus). Frequent, recurrent episodes of otitis media are most commonly observed in patients with selective IgA deficiency and decreased IgA or IgG subclass levels (especially IgG2)." Specific Antibody Deficiency (SAD) Antibody deficiency against microbial polysaccharide antigens is a well-established clinical entity and has been referred to as either antigen specific antibody deficiency (ASAD) or specific antibody deficiency (SAD)Q Frequent, recurrent episodes of otitis media are most commonly observed in patients with selective IgA deficiency and decreased IgA or IgG subclass levels (especially IgG2) Q. Frequent nfections were repoed in 92% of patients with SAD (sinusitis, 77%; pneumonia, 42%; otitis media,25%; bronchitis, 28%).