title: Antigen Concentrations as an Indicator of Clinical Remission and Disease Relapse in Cats with Histoplasmosis.
abstract: BACKGROUND
  Treatment monitoring is subjective and disease relapse is common in cats with histoplasmosis. The Histoplasma antigen enzyme immunoassay (EIA) is a noninvasive test used for determining disease remission and detecting disease relapse in humans with histoplasmosis. The utility of the antigen EIA for these purposes in cats remains unknown.
  
  
  OBJECTIVE
  Those Histoplasma antigen concentrations in urine and serum would decline with antifungal treatment and that antigen elimination would be an indicator of clinical remission in cats with histoplasmosis treated with antifungal treatment.
  
  
  METHODS
  Fifteen client-owned cats with histoplasmosis.
  
  
  METHODS
  Masked observational study. Cats were monitored monthly during antifungal treatment. Time of clinical remission and serum and urine antigen elimination were determined for each cat.
  
  
  RESULTS
  Twelve of 15 cats achieved clinical remission. At the time of diagnosis, antigen was detectable in urine in 14/15 (93%) cats and in serum in 11/15 (73%) cats. Both serum (P < .0005) and urine (P < .0001) antigen concentrations significantly decreased over time with effective treatment. Antigen elimination was sensitive [urine, 90.0% (95% CI 72.3-97.4%); serum, 90.4% (68.2-98.3%)] but less specific [urine, 64.6% (51.7-75.8%); serum, 52.1% (37.4-66.5%)] for disease remission. Urine antigen was positive in both cats and serum antigen was positive in 1 cat at the time of disease relapse.
  
  
  CONCLUSIONS
  Measurement of Histoplasma antigen in urine and serum might be useful tests for determining disease remission and relapse in cats with histoplasmosis. Further research is needed to investigate the importance of low-level antigenemia and antigenuria.
authors.affiliation: Department of Veterinary Clinical Sciences, Oklahoma State University, Stillwater, OK.
authors.forename: A S
authors.initials: AS
authors.lastname: Hanzlicek
authors.affiliation: Department of Veterinary Pathobiology, Oklahoma State University, Stillwater, OK.
authors.forename: J H
authors.initials: JH
authors.lastname: Meinkoth
authors.affiliation: MiraVista Diagnostics, Indianapolis, IN.
authors.forename: J S
authors.initials: JS
authors.lastname: Renschler
authors.affiliation: Department of Statistics, Oklahoma State University, Stillwater, OK.
authors.forename: C
authors.initials: C
authors.lastname: Goad
authors.affiliation: MiraVista Diagnostics, Indianapolis, IN.
authors.forename: L J
authors.initials: LJ
authors.lastname: Wheat
mesh_terms: D000818:Animals; D000935:Antifungal Agents / Q000627:therapeutic use; D000946:Antigens, Fungal / Q000097:blood*; D015415:Biomarkers; D002371:Cat Diseases / Q000097:blood*; D002415:Cats; D006658:Histoplasma / Q000378:metabolism*; D006660:Histoplasmosis / Q000097:blood / Q000188:drug therapy / Q000473:pathology / Q000662:veterinary*; D012008:Recurrence
chemical_list: D000935:Antifungal Agents; D000946:Antigens, Fungal; D015415:Biomarkers
keywords: Feline; Fungal; Histoplasma; Mycosis