Levels of IgG and IgM antibodies to L. pneumophila in exposed and nonexposed study groups, as determined by ELISA

GroupMedian IgG value in U/ml (range)Median IgM value in U/ml (range)
Factory employees12 (3-372)12b (1-238)
Exposed blood donors13 (1-109)16 (1-124)
Nonexposed blood donors11a (1-120)16 (1-124)
  • a Significantly lower than for factory employees (P = 0.002) and exposed blood donors (P = 0.001).

  • b Significantly lower than for exposed (P = 0.005) and nonexposed (P = 0.001) blood donors.