Description

Dear Editor,

We noted with interest Williams letter1 and the reply from the Editor regarding pneumococcal ELISAs. As clinicians struggling to interpret confusing results from a poorly standardised assay of serum IgG antibodies to a soup of 23 pneumococcal capsular polysaccharides, we wonder why clinical immunology laboratories do not use the standardised serotype-specific pneumococcal ELISAs which are routinely performed in clinical trials of multivalent pneumococcal conjugate vaccines2. The standard reference serum, 89SF, available from the FDA, provides assigned IgG, IgA and IgM antibody levels for 11 pneumococcal serotypes, and the ELISA method includes pre-adsorption of sera with pneumococcal C (cell wall) polysaccharide to remove this non-protective antibody. Results from such assays actually provide some information about the degree of protection of the patient against invasive pneumococcal infection and the immunological response to pneumococcal immunisation. Perhaps it is time to move on from U/ml to /ml of IgG to individual serotypes.

References:
1. Williams PE [Correspondence] CPD Bulletin Immunology and Allergy 2000; 1(2):64.
2. Quataert SA et al. Assignment of weight-based antibody units to a human anti-pneumococcal standard reference serum, lot 89-S. Clin Diagn Lab Immunol 1995; 2:590-597

Sincerely,