This study describes methods for extraction and quantification of calprotectin (L1 protein) in feces by enzyme immunoassay. This protein is a prominent antimicrobial component of neutrophils, monocytes, macrophages, and squamous epithelia. Calprotectin was stable in feces during storage for 7 days at room temperature. Small fecal samples taken from a 24-h feces collection gave a reliable estimate of calprotectin. Within-assay precision was 1.9%, and between-assay precision 14.8%. In healthy subjects (n = 33) median fecal calprotectin was 2025 micrograms/l and in hospital controls (n = 40) 10,500 micrograms/l. Median values in patients with Crohn's disease (n = 21) was 43,000 micrograms/l and in ulcerative colitis (n = 17) 40,000 micrograms/l. Fecal calprotectin was significantly correlated to fecal alpha 1-antitrypsin in the patients with Crohn's disease. Ten of 11 patients with gastrointestinal carcinomas had calprotectin level above the suggested reference limit of 6740 micrograms/l.

This study comprised 62 outpatients with ulcerative colitis who underwent 64 colonoscopies. The disease activity was evaluated according to endoscopic and histological criteria. The results revealed a significant correlation between both the endoscopic as well as the histological gradings of disease activity and faecal calprotectin. The median faecal calprotectin levels in the control group (6 mg/l) and in the patients with no or low disease activity (11.5 mg/l) were significantly different (p < 0.0001). The median calprotectin level among patients with active disease was 68 mg/l which was significantly different from the latter group (p < 0.0001). Furthermore, we suggest that the degree of inflammation rather than the extent of the disease determined the faecal calprotectin levels. In conclusion, assessment of faecal calprotectin seems to be a marker of disease activity in patients with ulcerative colitis.

In white cells correlated significantly with faecal calprotectin concentrations. In the group of 312 patients on NSAIDs faecal calprotectin concentrations were significantly higher than in controls, the prevalence of NSAID enteropathy being 44%. The prevalence and severity of NSAID enteropathy was independent of the particular type or dose of NSAID being taken or other patient variables. Conclusions-Assay of faecal calprotectin provides a simple practical method for diagnosing NSAID enteropathy in man. Forty four per cent of patients receiving these drugs had NSAID induced enteropathy when assessed by this technique; 20% of these had comparable levels of inflammation to that previously reported in patients with inflammatory bowel disease. (Gut 1999;45:362-366)