title: The intra-individual variability of faecal calprotectin: a prospective study in patients with active ulcerative colitis.
abstract: OBJECTIVE
  Leukocyte-derived proteins in faeces, especially calprotectin, are increasingly used to assess disease activity in ulcerative colitis. The objectives of the present study were to assess the importance of factors related to the stool sampling procedure.
  
  
  METHODS
  For 2 days, patients with active ulcerative colitis collected two stool samples at each bowel movement. The time of defecation, consistency and presence of blood were self-recorded in a diary. The variability in the concentrations of calprotectin during the day and between two consecutive days was assessed, as was the stability of calprotectin concentrations in samples stored at room temperature.
  
  
  RESULTS
  Altogether, 18 patients collected 287 stool samples. The intraclass correlation coefficient in pairs of samples from 132 bowel movements was 0.79 (95% CI 0.48-0.90). The median individual coefficient of variation in samples collected during the same day was 52% (4-178). There was a correlation between the level of calprotectin and the time between bowel movements (r = 0.5; p = 0.013). After 3 days at room temperature the calprotectin concentrations in stool samples were unchanged, but after 7 days a significant (p < 0.01) decrease was found (mean 28%; 95% CI 0.10-0.47).
  
  
  CONCLUSIONS
  The present data reveal a great variability in the concentrations of calprotectin in stool samples collected during a single day. Since the levels of calprotectin increased with longer time between the bowel movements, it seems most appropriate to analyse stool from the first bowel movement in the morning. Moreover, storage of stool samples at room temperature for more than 3 days is not advisable.
authors.affiliation: Department of Internal Medicine, Södra Älvsborgs Hospital, Borås, Sweden anders.lasson@vgregion.se.
authors.forename: Anders
authors.initials: A
authors.lastname: Lasson
authors.affiliation: Department of Internal Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Per-Ove
authors.initials: PO
authors.lastname: Stotzer
authors.affiliation: Department of Internal Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden Department of Biomedicine, Sahlgrenska Academy at the University of Gothenburg, Sweden.
authors.forename: Lena
authors.initials: L
authors.lastname: Öhman
authors.affiliation: Department of Biomedicine, Sahlgrenska Academy at the University of Gothenburg, Sweden Department of Internal Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Stefan
authors.initials: S
authors.lastname: Isaksson
authors.affiliation: Department of Biomedicine, Sahlgrenska Academy at the University of Gothenburg, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Sapnara
authors.affiliation: Department of Internal Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Hans
authors.initials: H
authors.lastname: Strid
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000032:analysis; D003093:Colitis, Ulcerative / Q000175:diagnosis* / Q000378:metabolism; D003113:Colonoscopy; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay; D005243:Feces / Q000737:chemistry*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D039841:Leukocyte L1 Antigen Complex / Q000032:analysis*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires; D055815:Young Adult
chemical_list: D015415:Biomarkers; D039841:Leukocyte L1 Antigen Complex
keywords: Calprotectin; Disease activity; Ulcerative colitis