Evaluation of Prevent ID and Quantum Blue rapid tests for fecal calprotectin.

BACKGROUND: Tests for fecal calprotectin are usually either enzyme-linked immunosorbent assays (ELISA) or a time-resolved fluorimetric immunoassay (TRFIA). These time-consuming tests are performed only once every 1 or 2 weeks. Before the results of the tests are known most patients have already undergone colonoscopy. A rapid test, performed on outpatients, could minimize the number of necessary colonoscopies. To establish optimal cut-off values minimizing the necessity for colonoscopies, we compared two commercially available rapid tests with a quantitative TRFIA. METHODS: Fecal samples were collected from 85 patients with lower gastrointestinal complaints. Calprotectin was measured using quantitative TRFIA as well as using two rapid tests: Prevent ID CalDetect and Quantum Blue calprotectin. We used the TRFIA method as the golden standard with a cut-off value of 50 µg/g. The percentage correct classification, sensitivity, specificity and positive and negative predictive value were calculated for both rapid tests at various cut-off levels. RESULTS: Correlation between both of the rapid tests with TRFIA was significant. Quantum Blue calprotectin (κ 0.77) correlated better than Prevent ID CalDetect (κ 0.46). Optimal cut-off levels for Prevent ID CalDetect and Quantum Blue calprotectin rapid tests were 15 µg/g and 40 µg/g with a reduction in the number of necessary colonoscopies of 39% and 62%, respectively. CONCLUSIONS: The Quantum Blue calprotectin rapid test demonstrated better analytical performance than the Prevent ID CalDetect in reducing the number of colonoscopies. Furthermore, the former test has the advantage of using a point of care reader for quantitative measurement and for establishing an optimal cut-off level.

Time-resolved fluorimetric immunoassay of calprotectin: technical and clinical aspects in diagnosis of inflammatory bowel diseases.

BACKGROUND: Growing evidence in the literature shows the clinical importance of the calprotectin assay in faeces, especially for the differential diagnosis and monitoring of patients with inflammatory bowel diseases. METHODS: We developed a time-resolved fluorimetric immunoassay for calprotectin to extend the limited measuring range of the commercially available ELISA method currently used in our laboratory. Together with the introduction of a non-enzymatic label, this new method offers the advantages of better precision and higher sensitivity. RESULTS: The new assay shows a dynamic measuring range extended by a factor four, which reduces the number of samples with concentrations outside the measuring range from 30% to only 4%. The value of the assay was confirmed in various patient groups suffering from active and inactive gastrointestinal diseases. We suggest that the frequent coincidence of a high calprotectin concentration with intestinal blood loss is not the consequence of mere blood loss, but can be ascribed to neutrophil infiltration and subsequent shedding into the intestinal lumen as a result of intestinal inflammation or malignancy. CONCLUSION: We expect that in the near future faecal calprotectin will be used as a non-invasive routine diagnostic marker and an effective laboratory parameter to monitor patients with inflammatory bowel disease.