title: Comparison of an indirect immunofluorescence assay, western blot analysis, and a commercially available ELISA for detection of Ehrlichia canis antibodies in canine sera.
abstract: OBJECTIVE
  To examine the correlation between results for an indirect immunofluorescence assay (IFA) that uses Ehrlichia canis antigen as a substrate (ie, E canis-IFA), 2 western blot (WB) analyses, and a commercially available ELISA in the detection of E canis antibody in dog sera.
  
  
  METHODS
  54 canine serum samples that were reactive on E canis-IFA and 16 canine serum samples that were E canis-IFA nonreactive.
  
  
  METHODS
  Serum samples were evaluated by use of 2 WB analyses and a commercially available ELISA. Correlation between results of the 3 testing modalities (ie, IFA, WB analyses, and the ELISA) was examined by use of nonreactive (E canis-IFA reciprocal titer, < 20), low-titer (reciprocal titer, 80 to 160), medium-titer (reciprocal titer, 320 to 2,560), and high-titer (reciprocal titer, 5,120 to > 20,480) serum samples.
  
  
  RESULTS
  For all serum samples in the nonreactive (n = 16), medium-titer (17), and high-titer (18) groups, correlation of results among IFA, WB analyses, and the commercially available ELISA was excellent. A poor correlation was found between IFA results and those of WB analyses and the ELISA for serum samples in the low-titer group (19), with only 4 of the 19 serum samples having positive results on both WB analyses and the commercially available ELISA.
  
  
  CONCLUSIONS
  The discrepancy between E canis-IFA, WB analyses, and the commercially available ELISA results for the low-titer serum samples may be related to a high IFA sensitivity or, more likely, a lack of specificity associated with cross-reactivity among Ehrlichia spp.
authors.affiliation: Department of Research and Development, IDEXX Laboratories Inc, 1 IDEXX Dr, Westbrook, ME 04092, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: O'Connor
authors.forename: Jancy L
authors.initials: JL
authors.lastname: Hanscom
authors.forename: Barbara C
authors.initials: BC
authors.lastname: Hegarty
authors.forename: Randall G
authors.initials: RG
authors.lastname: Groat
authors.forename: Edward B
authors.initials: EB
authors.lastname: Breitschwerdt
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D015153:Blotting, Western / Q000662:veterinary*; D004283:Dog Diseases / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D004285:Dogs; D041061:Ehrlichia canis / Q000276:immunology* / Q000302:isolation & purification; D016873:Ehrlichiosis / Q000097:blood / Q000175:diagnosis / Q000276:immunology / Q000662:veterinary*; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary*; D019084:Fluorescent Antibody Technique, Indirect / Q000662:veterinary*
chemical_list: D000907:Antibodies, Bacterial