title: Clinical importance of faecal calprotectin variability in inflammatory bowel disease: intra-individual variability and standardisation of sampling procedure.
abstract: OBJECTIVE
  Faecal (f-) calprotectin is a biomarker of intestinal inflammation. Previous studies have described intra-individual day-to-day variability of this biomarker in patients with inflammatory bowel disease (IBD) and morning samples have been suggested for standardisation purposes. With this project, we investigated if day-to-day variability differed from diurnal variability. Additionally, we evaluated a new extraction method for f-calprotectin analysis.
  
  
  METHODS
  Fifty patients provided three faeces samples from morning - evening - morning on two consecutive days. Nineteen patients provided two faeces samples from the same bowel movement, one conventional spot sample, and one sample with a device for patient-administered sampling and extraction.
  
  
  RESULTS
  The two morning samples differentiated between mucosal inflammation and mucosal healing with same level of agreement as the two samples from the same day (kappa 0.76), using an f-calprotectin cut-off level of 259 μg/g. Although large intra-individual variation in f-calprotectin values, there were no significant day-to-day (p = 0.096) or diurnal variation (p = 0.78). Used by laboratory technicians, the new extraction device correlated significantly with the conventional extraction method (p < 0.001), Spearman's rank correlation coefficient 0.95. Of the 19 patients testing patient administered extraction, two patients provided samples leading to considerably higher f-calprotectin levels than conventional sampling procedure.
  
  
  CONCLUSIONS
  The reliability of f-calprotectin morning samples is equal to the reliability of samples from different bowel movements on the same day. The new extraction method is reliable when used by laboratory technicians, but larger studies are recommended to evaluate patient administered extraction.
authors.affiliation: a Department of Medicine , Unger-Vetlesen's Institute, Lovisenberg Diaconal Hospital , Oslo , Norway ;|b Institute of Clinical Medicine , University of Oslo , Oslo , Norway ;
authors.forename: Vendel
authors.initials: V
authors.lastname: Kristensen
authors.affiliation: a Department of Medicine , Unger-Vetlesen's Institute, Lovisenberg Diaconal Hospital , Oslo , Norway ;
authors.forename: Gunn Helen
authors.initials: GH
authors.lastname: Malmstrøm
authors.affiliation: a Department of Medicine , Unger-Vetlesen's Institute, Lovisenberg Diaconal Hospital , Oslo , Norway ;
authors.forename: Viggo
authors.initials: V
authors.lastname: Skar
authors.affiliation: c Department of Medicine, Section of Gastroenterology , Lovisenberg Diaconal Hospital , Oslo , Norway ;
authors.forename: Arne
authors.initials: A
authors.lastname: Røseth
authors.affiliation: b Institute of Clinical Medicine , University of Oslo , Oslo , Norway ;|d Department of Gastroenterology , Oslo University Hospital , Oslo , Norway.
authors.forename: Bjørn
authors.initials: B
authors.lastname: Moum
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000032:analysis; D002940:Circadian Rhythm / Q000502:physiology*; D003113:Colonoscopy / Q000379:methods / Q000592:standards*; D004797:Enzyme-Linked Immunosorbent Assay; D005243:Feces / Q000737:chemistry*; D005260:Female; D006801:Humans; D015212:Inflammatory Bowel Diseases / Q000175:diagnosis / Q000378:metabolism* / Q000503:physiopathology; D007413:Intestinal Mucosa / Q000378:metabolism; D039841:Leukocyte L1 Antigen Complex / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012720:Severity of Illness Index; D055815:Young Adult
chemical_list: D015415:Biomarkers; D039841:Leukocyte L1 Antigen Complex
keywords: Biological markers; Crohn disease; enzyme-linked immunosorbent assay; faeces; inflammatory bowel diseases; leukocyte L1 antigen complex; ulcerative colitis