title: Laboratory diagnosis of Legionnaires' disease.
abstract: Legionnaires' disease was diagnosed in 32 patients with nosocomially acquired pneumonia by using direct immunofluorescence examination of respiratory tract secretions, indirect immunofluorescence determinations of antibody titer, and/or culture of Legionella pneumophila from respiratory tract secretions. Cultures of specimens for Legionella pneumophila were positive for 13 of 21 patients for whom appropriate specimens were submitted. Using a positive culture as a definition of Legionnaires' disease, the sensitivity of direct immunofluorescence examination was 62%; that of indirect immunofluorescence serologic studies, 75%. Using any positive test as a definition of Legionnaires' disease, the sensitivity of direct immunofluorescence examination of respiratory tract secretions was 50%, that of indirect immunofluorescence serologic studies (using all 4 serogroups), 80%; that of culture, 65%. A negative control group of 21 patients without Legionnaires' disease was used to estimate the specificity of the tests. The specificity of direct immunofluorescence examination was 94%; that of indirect immunofluorescence serologic studies, 75%. Culture of specimens was necessary to diagnose some cases of Legionnaires' disease because the other 2 tests were negative. All 3 tests should be performed for optimal sensitivity and specificity.
mesh_terms: D000907:Antibodies, Bacterial / Q000032:analysis; D001419:Bacteria / Q000276:immunology / Q000302:isolation & purification; D001431:Bacteriological Techniques; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D006801:Humans; D007877:Legionnaires' Disease / Q000175:diagnosis* / Q000276:immunology / Q000382:microbiology; D013183:Sputum / Q000276:immunology / Q000382:microbiology
chemical_list: D000907:Antibodies, Bacterial