DIAGNOSIS OF STREPTOCOCCUS-PNEUMONIAE PNEUMONIA BY QUANTITATIVE ENZYME-LINKED-IMMUNOSORBENT-ASSAY OF C-POLYSACCHARIDE ANTIGEN

Aims-To evaluate the use of a quantitative enzyme linked immunosorbent assay (ELISA) detecting C-polysaccharide (PnC) antigen in sputum for the diagnosis of Streptococcus pneumoniae infection. Methods-Specimens of sputum from 60 patients with acute community and hospital acquired pneumonia and infective exacerbations of obstructive airways disease were examined by semiquantitative culture and antigen ELISA. Results-Using a cutoff value of 1 mu g/ml PnC antigen for a positive result, the sensitivity of this assay was 90.3%, specificity 93.1%, predictive value of a positive result was 93.5%, and the predictive value of a negative result 89.6%. Conclusions-Quantitation of C-polysaccharide antigen in sputum by ELISA distinguishes between carriage of oral bacteria which express PnC-like antigen and infection with S pneumoniae and compares favourably with other diagnostic methods.