Evaluation of Different Extraction- and Analysis Methods for Calprotectin in Feces

Background Calprotectin is a protein expressed in the cytoplasm inside the neutrophile granulocytes. During inflammatory bowel disease (IBD), the neutrophile granulocytes are involved in a complex interaction at the inflammatory area where they die and release their content into the intestinal lumen. Therefore, calprotectin in stool is a suitable marker for diagnosis and measurement of the disease-activity in patients with IBD. The most commonly used method to detect calprotectin in stool is ELISA, but the process of manual preparation of stool samples is time-consuming. Aim The objective of the study was to evaluate an extraction method that could replace manual preparation of fecal samples and to compare different methods for measuring Calprotectin in stool using two ELISA-methods from two manufacturers and one rapidtest. Methods For extraction of calprotectin from stool samples we used sample collector tubes from Epitope Diagnostics and fecal preparation kits from Roche. Two different ELISA-kits for measuring calprotectin concentration in stool were compared. Measurements of calprotectin with rapid-test from Epitope Diagnostics were also performed and were compared with the two ELISA kits. Results The results indicate a poor correlation between two extraction methods with Sample Collector Tube and Roche preparation kit. The comparison between the two ELISA-kits showed poor correlation. Evaluation of rapid test showed 33% false negative results with a cut-off value at 50 mg/kg. Conclusion Evaluation of products from Epitope Diagnostics showed poor correlation with the Bühlmann ELISA and an unreliable rapid test. Therefore, none of evaluated products from Epitope Diagnostics is accurate enough to be used for clinical diagnosis in the laboratory