title: Heat treatment prior to testing allows detection of antigen of Dirofilaria immitis in feline serum.
abstract: BACKGROUND
  Diagnosis of Dirofilaria immitis infection in cats is complicated by the difficulty associated with reliable detection of antigen in feline blood and serum samples.
  
  
  METHODS
  To determine if antigen-antibody complex formation may interfere with detection of antigen in feline samples, we evaluated the performance of four different commercially available heartworm tests using serum samples from six cats experimentally infected with D. immitis and confirmed to harbor a low number of adult worms (mean = 2.0). Sera collected 168 (n = 6), 196 (n = 6), and 224 (n = 6) days post infection were tested both directly and following heat treatment.
  
  
  RESULTS
  Antigen was detected in serum samples from 0 or 1 of 6 infected cats using the assays according to manufacturer's directions, but after heat treatment of serum samples, as many as 5 of 6 cats had detectable antigen 6-8 months post infection. Antibodies to D. immitis were detected in all six infected cats by commercial in-clinic assay and at a reference laboratory.
  
  
  CONCLUSIONS
  These results indicate that heat treatment of samples prior to testing can improve the sensitivity of antigen assays in feline patients, supporting more accurate diagnosis of this infection in cats. Surveys conducted by antigen testing without prior heat treatment of samples likely underestimate the true prevalence of infection in cats.
authors.affiliation: Department of Veterinary Pathobiology, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA. susan.little@okstate.edu.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Little
authors.forename: Melissa R
authors.initials: MR
authors.lastname: Raymond
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Thomas
authors.forename: Jeff
authors.initials: J
authors.lastname: Gruntmeir
authors.forename: Joe A
authors.initials: JA
authors.lastname: Hostetler
authors.forename: James H
authors.initials: JH
authors.lastname: Meinkoth
authors.forename: Byron L
authors.initials: BL
authors.lastname: Blagburn
mesh_terms: D000818:Animals; D000947:Antigens, Helminth / Q000097:blood*; D002371:Cat Diseases / Q000175:diagnosis* / Q000276:immunology*; D002415:Cats; D004183:Dirofilaria immitis / Q000276:immunology*; D004184:Dirofilariasis / Q000175:diagnosis* / Q000276:immunology*; D005260:Female; D006358:Hot Temperature; D008297:Male
chemical_list: D000947:Antigens, Helminth