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 mu g/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 (kappa 0.77) correlated better than Prevent ID CalDetect (kappa 0.46). Optimal cut-off levels for Prevent ID CalDetect and Quantum Blue calprotectin rapid tests were 15 mu g/g and 40 mu g/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.