Stability of Legionella urinary antigens over time.

Twenty-two urine samples positive for Legionella pneumophila serogroup 1 antigen by EQUATE radioimmunoassay (RIA) (Binax, Portland, ME, USA) were stored at various temperatures and the RIA repeated at 1, 7, 30, 90, and 120 days to evaluate stability of the urinary antigens. The mean ratios of patient/negative control remained stable. Although there was a 10% decrease in the mean ratios after 1 month, changes were not significant. However, individual samples with ratios close to 3 may fall to < 3.