Assessment of the Neutrophil Dominating Protein Calprotectin in Feces: A Methodologic Study

Abstract

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.