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

ABSTRACT

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.