Recent advances in the diagnosis of serogroup 1 L. pneumophila pneumonia by detection of urinary antigen.

ELISA and radioimmunoassay were analyzed for their ability to detect antigen in urine from patients with serogroup 1 Legionnaires' disease. The sensitivity of the two assays is approximately 80 percent, and the specificity is estimated to be 99 percent or better. Assay predictive values, determined on 1,239 specimens, were 76 percent for positive, and 99 percent for negative results. Antigen was detected nearly as often during the first three days of symptoms as later. Antigen excretion lasted from four to 327 days. A latex agglutination test detected antigen in 82 percent of patients positive by the other immunoassays.