Immunological testing in non-cystic fibrosis bronchiectasis.

The review of non-cystic fibrosis bronchiectasis by Smith elegantly highlights the lack of evidence available in some areas. In particular, approach to immunological testing is varied. Table 2 on page 134 in this review describes the diagnostic features required for immunodeficiency (including immunoglobulin G [IgG] subclass 2 deficiency amongst other IgG subclass deficiencies). However, IgG subclass testing has not been favoured by recent national guidelines, because IgG subclass deficiency can occur in well, asymptomatic individuals with normal functional antibody responses (due to heavy-chain deletions), and this therefore gives no information on functional antibody response to particular antigens. Rather, the British Thoracic Society advocates functional testing to peptide and polysaccharide antigens, as well as measurement of serum IgG, immunoglobulin A (IgA) and immunoglobulin M (IgM) in the routine assessment of possible antibody deficiency before more detailed second line tests are considered.