title: [Accuracy and diagnostic utility of IgM in Bartonella henselae infections].
abstract: BACKGROUND
  Laboratory diagnosis of cat scratch disease (CSD) is based on the determination of specific antibodies anti-Bartonella henselae by different techniques. The CDC recommends IgG by immunofluorescent assay (IFA) as the gold standard.
  
  
  OBJECTIVE
  To determine the accuracy and diagnostic utility of anti-B.henselae IgM by IFA for CSD.
  
  
  METHODS
  Anti-B. henselae IgG was determined in serum of 108 patients with CSD suspicion; in addition, specific IgM was determined separately and blindly by two thoroughly trained laboratory professionals. We calculated sensitivity (S), specificity (Sp), predictive values both positive (PPV) and negative (NPV), and likelihood ratio (LR) for IgM positive (LR +) and negative (LR-).
  
  
  RESULTS
  In 37 patients with positive anti-B.henselae IgG, IgM was positive in 16 and negative in 21; in 71 patients with negative IgG, IgM was negative in 69 and positive in 2. Therefore, IgM showed S 43%, E 97%, PPV 88%, NPV 77%, LR (+) 15 and LR (-) 0.58.
  
  
  CONCLUSIONS
  The results show that a positive IgM supports, but a negative one does not rule out a B. henselae infection. Therefore, IgG should be still considered as the gold standard for the diagnosis of CSD.
authors.affiliation: División de Pediatría, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile. katia@med.puc.cl
authors.forename: Katia
authors.initials: K
authors.lastname: Abarca
authors.forename: Matías
authors.initials: M
authors.lastname: Winter
authors.forename: Delphine
authors.initials: D
authors.lastname: Marsac
authors.forename: Carlos
authors.initials: C
authors.lastname: Palma
authors.forename: Ana M
authors.initials: AM
authors.lastname: Contreras
authors.forename: Marcela
authors.initials: M
authors.lastname: Ferrés
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D018416:Bartonella henselae / Q000276:immunology*; D001688:Biological Products / Q000097:blood; D002372:Cat-Scratch Disease / Q000175:diagnosis* / Q000276:immunology; D002415:Cats; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D007075:Immunoglobulin M / Q000097:blood*; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D000907:Antibodies, Bacterial; D001688:Biological Products; D007074:Immunoglobulin G; D007075:Immunoglobulin M