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P120. The concentrations of calprotectin in stool samples vary during the day in patients with active ulcerative colitis

A. Lasson1, P.-O. Stotzer2, L. Öhman2, S. Isaksson2, H. Strid2, 1Södra Älvsborgs Hospital, Department of Internal Medicine, Borås, Sweden, 2Sahlgrenska University Hospital, Department of Internal Medicine, Gothenburg, Sweden

Background

The levels of leukocyte-derived proteins in faeces are increasingly used to assess disease activity in inflammatory bowel diseases. Calprotectin is the most commonly used faecal marker of intestinal inflammation. However, the variability over the day and the importance of factors related to the sampling procedure have not been elucidated.

Methods

Over a period of 2 days, patients with active ulcerative colitis collected two samples of faeces at each bowel movement. Patients with proctitis were excluded. Time of defecation, consistency and presence of blood were self-recorded in a diary. Variability of the concentrations of calprotectin during the day were assessed as was the stability of calprotectin concentrations in the samples up to 7 days in room temperature. In a questionnaire, the patients reported how they experienced the sampling procedure.

Results

Altogether, 18 patients, median age 43 (18–73) years, with mild to moderately active ulcerative colitis, collected 287 stool samples during 35 days. The IntraClass Correlation Coefficient in pairs of samples taken at 132 different bowel movements was 0.79. The mean individual coefficient of variation (CV) in samples collected during the same day was 62.4% (SD 36.3). In 6 patients the calprotectin values fluctuated below 250 µg/g and in 3 patients below 100 µg/g during the day. There was a correlation between the level of calprotectin and the time between bowel movements (p = 0.013). The level of calprotectin also correlated with the faecal consistency (p = 0.01).

There was no significant difference in calprotectin concentrations between samples stored at room temperature for one day and three days. However, after 7 days in room temperature a significant (p < 0.01) decrease of calprotectin concentrations was found (mean 28%; 95% CI 0.10–0.47).

Overall, the result of the questionnaire demonstrated that the patients did not find the stool sampling procedure burdensome.

Conclusion

In patients with active ulcerative colitis, the faecal concentrations of calprotectin vary considerably and clinically significantly during the day. In some patients even below the level quoted as normal. The levels of calprotectin seem to be influenced by the faecal consistency and the time between bowel movements. In samples collected at the same bowel movement, the correlation was good. Storage of samples in room temperature for more than 3 days is not advisable. The stool sampling procedure is important and more efforts should be made to find a standardized way to do it.