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.

Calprotectin, a prominent cytosol protein in neutrophil granulocytes, was present in increased concentrations in stools from 50 of 53 patients with colorectal cancer, 32 of 40 patients with colorectal polyps, and all of 18 patients with gastric cancer. After radical surgery, faecal calprotectin levels reverted to the normal range in all but one patient with colorectal cancer. Calprotectin determinations are simplified by the stability of this protein in stools. Reliable estimates can be obtained in samples of only 5 g. On the basis of data from the literature, the test for calprotectin seems better than that for occult blood for the detection of gastrointestinal neoplasms.

No abstract

Measurement of fecal calprotectin may become a diagnostic tool in detecting colorectal carcinoma. The specificity in relation to colorectal carcinoma has not, however, been completely investigated. Both neoplastic and inflammatory conditions may be associated with elevated values; therefore, it is unlikely that calprotectin can predict specific colonic disorders.