Diagnosis of chronic Pseudomonas aeruginosa infection in cystic fibrosis by enzyme-linked immunosorbent assay.

An easily applicable test for diagnosis of chronic Pseudomonas aeruginosa infection in cystic fibrosis by enzyme-linked immunosorbent assay (ELISA) for determination of serum immunoglobulin G to P. aeruginosa was developed. Soluble antigens obtained by ultrasonication of P. aeruginosa, serotypes O:1 to O:17, were used as antigens immobilized to polystyrene microtiter plates. The intraplate, plate-to-plate, and day-to-day variations were 14, 19, and 20%, respectively. Plates coated with the antigens could be stored for at least 64 days at +4 and +22 degrees C without any significant change in activity. Normal values were determined in sera from 164 controls (100 children and 64 adults). The sensitivity and specificity of the ELISA was determined by using serum samples from 243 cystic fibrosis patients and were compared to results with crossed immunoelectrophoresis (CIE). The ELISA could diagnose chronic P. aeruginosa infection with a diagnostic sensitivity of 93% and specificity of 92%. The sensitivity and specificity for the diagnosis of the early stages of chronic P. aeruginosa infection by a single sample were 90 and 100%, respectively, and by using an increased antibody response in paired samples, the sensitivity was 93% and specificity was 87%. There was a statistically significant correlation between antibody levels obtained by ELISA and those obtained by CIE. The sensitivity and specificity of the ELISA were equal to those of CIE, and because of its simplicity, the ELISA is recommended as a routine test in patients with cystic fibrosis.