title: A proposed reference change value for an IgA anti-tissue transglutaminase immunoassay to improve interpretation of serial results in celiac patients.
abstract: BACKGROUND
  Celiac disease (CD) is an autoimmune disorder caused by an inappropriate immunological response to gluten ingestion in genetically susceptible individuals. IgA anti-tissue transglutaminase (tTG) antibodies have been widely employed as a specific biochemical marker for CD. Recent studies have also shown its usefulness in evaluating patient compliance with a gluten-free diet.
  
  
  METHODS
  A group of 28 subjects with CD was selected for the study. Each fulfilled the requirement of a gluten-free diet for more than one year. IgA anti-tTG determination was performed every two months for half a year. These data were used to estimate the biological variation (BV) of IgA anti-tTG in celiac patients and to calculate the reference change value (RCV).
  
  
  RESULTS
  The within-subject biological variation (CVI) and between-subject biological variation (CV(G)) were 19.2% and 75.6%, respectively, and the index of individuality was 0.25. The RCV calculated using these data together with our analytical imprecision (5.7%) was 55.5% for a 95% level of significance.
  
  
  CONCLUSIONS
  We have determined for the first time the BV and the RCV for IgA anti-tTG in a celiac population. This value and the probability curve generated from our data could be a valuable tool for monitoring patients' adherence to dietary treatment.
authors.affiliation: Laboratory of Clinical Chemistry, Virgen de la Salud Hospital, Complejo Hospitalario de Toledo, Toledo, Spain. ejlaserna@sescam.jccm.es
authors.forename: Emilio José
authors.initials: EJ
authors.lastname: Laserna-Mendieta
authors.forename: Daniel
authors.initials: D
authors.lastname: Pineda-Tenor
authors.forename: Jesús
authors.initials: J
authors.lastname: Timón-Zapata
authors.forename: Julián Fabián
authors.initials: JF
authors.lastname: Carretero-Gómez
authors.forename: Julio
authors.initials: J
authors.lastname: Valle-Muñoz
authors.forename: Manuel
authors.initials: M
authors.lastname: Gómez-Serranillos
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002446:Celiac Disease / Q000097:blood* / Q000175:diagnosis / Q000178:diet therapy / Q000276:immunology; D055050:Diet, Gluten-Free; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D007070:Immunoglobulin A / Q000097:blood*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010349:Patient Compliance; D012016:Reference Values; D012680:Sensitivity and Specificity; D011503:Transglutaminases / Q000276:immunology
chemical_list: D007070:Immunoglobulin A; D011503:Transglutaminases