Legionnaire's Disease: A Clinical Diagnostic Approach.

Legionnaire's disease is a nonzoonotic atypical pneumonia caused by Legionella sp that occurs sporadically or in outbreaks. Legionnaire's disease pneumonia is accompanied by several extrapulmonary clinical and laboratory findings. Rather than testing all pneumonias for Legionnaire's disease, the clinical challenge is to recognize the diagnostic significance of Legionnaire's disease's. The pretest probability of Legionnaire's disease is increased if several characteristic extrapulmonary findings are present. Similarly, if certain key findings are absent, Legionnaire's disease may be eliminated from further diagnostic consideration. If characteristic clinical findings are present, then specific tests should be ordered to confirm or rule out Legionnaire's disease.