Re:Specific antibody deficiency in children with chronic wet cough
Lim et al(1) understandably interpret the results of their retrospective study with caution. However they only consider one possible chain of causation in seeking to explain their findings, namely that children with worse chest radiographs who made poorer antibody responses did so as a consequence of an underlying primary immunodeficiency. An alternative explanation would be that previous, chronic lower and/or upper respiratory tract infection with pneumococci of the relevant serotypes had induced hyporesponsiveness to the corresponding polysaccharide antigens. This has previously been shown with respect to responses to conjugated polysaccharide antigens in children with documented previous colonisation (2). The way children respond to these antigens may have more to do with their personal history of infection than their genetics. References 1. Lim MT, Jeyarajah K, Jones P, et al. Specific antibody deficiency in children with chronic wet cough. Arch Dis Child. 2012; 97:478-80 2. Dagan R, Givon-Lavi N, Greenberg D, Fritzell B, Siegrist CA. Nasopharyngeal carriage of Streptococcus pneumoniae shortly before vaccination with a pneumococcal conjugate vaccine causes serotype-specific hyporesponsiveness in early infancy. J Infect Dis 2010; 201:1570-9
Conflict of Interest:
AF undertakes clinical research, educational and advisory work for vaccine manufacturers including those making pneumococcal vaccines but receives no personal remuneration for this. All funding is paid to his employers.
The importance of thorough investigation of children with chronic wet cough
We read with interest the recent paper by Lim et al. reporting the prevalence of specific polysaccharide antibody deficiency in a cohort of 96 children with chronic wet cough. Specific polysaccharide antibody deficiency was defined in terms of inadequate pneumococcal serotype- specific antibody levels following immunisation with Prevenar and/or Pneumovax II. Results of other immunological investigations were not provided other than they had normal total immunoglobulin G levels.
We consider that it is important to investigate children with apparently inadequate responses to pneumococcal immunisation more thoroughly because poor antibody responses may be a feature of other specific immunological conditions. We would also argue that the label of "chronic wet cough" is an imprecise term. Lim et al. do not specify the proportion of children who underwent bronchoscopy and bronchoalveolar lavage in their cohort. If a child has sufficient chronic symptoms sufficient to warrant further investigations including immunological assessment then flexible fibreoptic bronchoscopy and bronchoalveolar lavage (BAL) should be considered routinely. BAL culture is the 'gold standard' to diagnose bacterial lower respiratory tract infection in this situation. Sputum is rarely obtained from younger children and cough swabs may not reflect lower airway microbiology accurately.
Zgherea et al. recently reported bronchoscopic findings in 197 children with chronic wet cough. In this study 46% of BAL samples were positive for respiratory bacterial pathogens and there was also a high incidence of structural airway abnormalities, including laryngomalacia and/or tracheomalacia in 30% of children aged 3 years.
We therefore believe that careful clinical assessment of children with "chronic wet cough" is indicated. This should include both immunological investigations and bronchoscopy in order to confirm bacterial infection and to identify any structural airway abnormalities.
1. Lim MT, Jeyarajah K, Jones P, et al. Specific antibody deficiency in children with chronic wet cough. Arch Dis Child. Online First: 30 January 2012. doi:10.1136/archdischild-2011-300691
2. Driessen G, van der Burg M. Educational paper: primary antibody deficiencies. Eur J Pediatr. 2011;170:693-702
3. Equi AC, Pike SE, Davies J, et al. Use of cough swabs in a cystic fibrosis clinic. Arch Dis Child. 2001;85:438-9
4. Zgherea D, Pagala S, Mendiratta M, et al. Bronchoscopic findings in children with chronic wet cough. Pediatrics. 2012;129:e364-9
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