MEASUREMENT OF SPUTUM ANTIBODIES IN THE DIAGNOSIS OF ACUTE AND CHRONIC RESPIRATORY-INFECTIONS ASSOCIATED WITH CHLAMYDIA-PNEUMONIAE

The aim of this study was to develop methods for the measurement of sp utum antibodies in the laboratory diagnosis of acute and chronic lower respiratory tract infections caused by Chlamydia pneumoniae. Paired s erum specimens, sputum specimens, and pharyngeal or nasopharyngeal swa bs were obtained from 97 patients; 51 of them had community-acquired p neumonia, and 46 had chronic obstructive pulmonary disease (COPD). C. pneumoniae-specific serum immunoglobulin G (IgG), IgA, and IgM antibod ies were measured by the microimmunofluorescence (micro-IF) test. For sputa, specific IgA and IgG antibodies were measured by the micro-IF t est and secretory IgA (sIgA) was measured by enzyme immune assay (EIA) with C. pneumoniae elementary bodies as the,antigen, Sputun IgA and s IgA antibodies to C. pneumoniae were found, respectively, in 52 and 51 % of the COPD patients, Elevated levels of stable serum IgG and IgA an tibodies (IgG titer of greater than or equal to 128 and IgA titer of g reater than or equal to 40), suggesting chronic infection, were found in 54% of the COPD patients, The sensitivity for the sputum IgA micro- IF test compared with elevated serum antibody levels was 87.5%, and th at for the sputum sIgA EIA was 88%; the respective specificities were 90 and 950/0. Acute C. pneumoniae infection was diagnosed in seven pne muonia patients, and two (29%) of these patients were positive by sput um EIA antibody measurements, Two pneumonia patients without acute inf ection had stable elevated IgG and IgA levels in their sera, and both of them were sputum antibody positive, We conclude that the measuremen t of IgA antibodies to C. pneumoniae in sputum is a useful additional diagnostic tool for chronic C. pneumoniae infections.