Aims: Objective of this study was to compare the assay characteristics of a new fecal calprotectin rapid test with an enzyme-linked immunosorbent assay (ELISA). The second aim was to assess the potential of measuring fecal calprotectin as screening method for intestinal inflammation and colorectal malignancies.
Patients and methods: One hundred forty patients with lower gastrointestinal symptoms referred to colonoscopy provided fecal samples (56, control group; 18, diverticulosis; 29, colorectal adenoma; 8, colorectal carcinoma (CRC); 18, active inflammatory bowel disease (IBD); 11, intestinal infections). Feces were analyzed by two assay methods.
Results: Compared to the control group (median 25.8 microg/g), calprotectin levels were significantly increased in adenoma (66.3 microg/g), CRC (164 microg/g), intestinal infections (306 microg/g), and active IBD (797 microg/g). An adequate diagnostic accuracy could be found for active IBD with a sensitivity, specificity, and an area under the curve (AUC) of 100%, 79%, and 0.955 (ELISA) vs. 89%, 80%, and 0.896 (rapid test). Similar results were obtained for CRC (100%, 79%, 0.922 vs. 100%, 80%, 0.948) whereas in adenomas a low sensitivity, specificity, and AUC of 55%, 79%, and 0.686 vs. 52%, 80%, and 0.666 were found for fecal calprotectin.
Conclusions: Both fecal calprotectin assays are effective in identifying active IBD and CRC but lack analytical sensitivity in separating CRC from adenoma as well as adenoma from the control group. The new calprotectin rapid test is a convenient method for assessing the calprotectin level in an outpatient setting. Henceforth, it provides a precondition for the fecal calprotectin method to challenge fecal occult blood testing in further evaluations.