title: Legionella pneumophila serogroup 1 antibody kinetics in patients with Legionnaires' disease: implications for serological diagnosis.
abstract: To evaluate current serological criteria for Legionella pneumophila serogroup 1 (Lp1), the antibody response was prospectively studied in all patients hospitalized for Legionnaires' disease in a Swedish county during 11 y (n = 62). A 4-fold or greater rise in antibody titre to > or = 128 (the minimum convalescent antibody level for diagnosis, as recommended by the Centers for Disease Control and Prevention), using the indirect immunofluorescence antibody test, was found in 21/52 (40%) of tested patients. By referring to the titre levels in healthy residents from the local population (World Health Organization criteria), 45/52 (87%) cases were confirmed serologically. In 21 patients followed longitudinally for 10 y, the median antibody titre fell from 256 (range 32-1024) to 16 (range 2-128) in 3 y. No booster reactions were observed in any patient. After 10 y, the geometric mean titre of this clinical cohort had reached the same level as observed in the background population 5 y earlier. Titre levels in subjects exposed to Legionella from a municipal water system indicate that only 1 out of 10 of all infections are identified clinically. Indirect immunofluorescent antibody testing with local reference sera is a sensitive method for laboratory confirmation of Lp1 in an unselected pneumonia population.
authors.affiliation: Department of Infectious Diseases, Ryhov Hospital, Jönköping, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Darelid
authors.forename: Sture
authors.initials: S
authors.lastname: Löfgren
authors.forename: Bo-Eric
authors.initials: BE
authors.lastname: Malmvall
authors.forename: Margreth-Ann
authors.initials: MA
authors.lastname: Olinder-Nielsen
authors.forename: Gunnar
authors.initials: G
authors.lastname: Briheim
authors.forename: Hans
authors.initials: H
authors.lastname: Hallander
mesh_terms: D000907:Antibodies, Bacterial / Q000032:analysis / Q000097:blood*; D000917:Antibody Formation; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D016952:Legionella pneumophila / Q000276:immunology* / Q000302:isolation & purification; D007877:Legionnaires' Disease / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology*; D008297:Male; D011446:Prospective Studies; D012016:Reference Values; D012307:Risk Factors; D012680:Sensitivity and Specificity; D016036:Seroepidemiologic Studies; D012698:Serologic Tests / Q000379:methods; D013548:Sweden / Q000453:epidemiology
chemical_list: D000907:Antibodies, Bacterial