Faecal calprotectin levels in a high risk population for colorectal neoplasia

Background-Faecal concentrations of the protein calprotectin have been foun d to be elevated in patients with colorectal neoplasia, suggesting that it might be used as a screening tool for colorectal cancer as well as adenomas . Aims-To measure the sensitivity and specificity of faecal calprotectin for the detection of adenomas in high risk individuals undergoing colonoscopy. Also, to investigate between and within stool variability of calprotectin c oncentrations. Subjects-A total of 814 patients planned for colonoscopy were included for the following indications: positive faecal occult blood test, 25; neoplasia surveillance, 605; newly detected polyp, 130; and family risk, 54. Methods-Two faecal samples from each of two stools were analysed using the PhiCal ELISA test device (Nycomed Pharma AS). Results-Adenoma patients had significantly higher calprotectin levels than normal subjects (median 9.1 (95% confidence interval 7.5-10.1) v 6.6 (5.6-7 .4)mg/l). There was no significant decrease in calprotectin levels after po lypectomy. Levels in cancer patients were significantly higher than those i n all other subgroups (median 17.6 mg/l (11.5-31.0)). With a cut off limit of 10 mg/l, the sensitivity for cancer was 74% and for adenoma 43%. Corresp onding specificity values were 64% for no cancer and 67% for no neoplasia ( cancer+adenoma). Specificity varied from 71% for one stool sample to 63% fo r four samples. Stool variability was small, suggesting that two spots from one stool were as discriminative as two spots from each of two stools. Conclusions-The sensitivity and specificity of faecal calprotectin levels a s a marker for colorectal adenoma and carcinoma justifies its use in high r isk groups, but specificity is too low for screening of average risk person s. Lack of a decrease in levels after polypectomy may be due to a more wide spread leucocyte migration into the intestinal lumen than that at the polyp site, and needs further investigation.