P374 Home or hospital-based analysis of stool calprotectin: assessing two methods for monitoring inflammatory bowel disease

Abstract

Background and aims: Repeated stool calprotectin measurements are increasingly used to monitor asymptomatic patients with inflammatory bowel diseases. Recently a lateral flow-based rapid test was launched that allows patients to measure stool calprotectin values at home. It comes together with a software application (IBDoc®) that turns a smartphone camera into a reader. We compared this new, by patients, performed method with the hospital-based lateral flow reader Quantum Blue®(QB) and the enzyme-linked immuno sorbent assay (ELISA) to see whether these tests agreed sufficiently. Methods: In a single center method comparison study, we asked 101 teenagers and adults to perform the IBDoc® measurement at home. Next the residual of the extraction fluid and a fresh specimen from the same bowel movement were sent to our hospital where they were tested with the QB reader and ELISA respectively. Results: We received 152 IBDoc® results, 138 residuals for QB reading and 170 fresh stool samples for ELISA analysis. Spearman's rank correlation coefficient was 0.94 for IBDoc® versus QB and 0.85 for IBDoc® versus ELISA. In the low range of calprotectin (<500 μg/g) 91% of IBDoc®-QB pairs were within predefined limits of agreement (+/-100 μg/g), and 71% of IBDoc®-ELISA pairs. In the high range (≥ 500 μg/g) respectively 81% and 64% of pairs were within limits of agreement (+/-200 μg/g). Conclusions: We found sufficient agreement between the home-used lateral flow method and the established FC tests in the lower ranges of calprotectin. We suggest that confirmation of high IBDoc® readings is done before therapy adjustment is considered. Misclassification will probably further reduce when patients do their first IBDoc® test under close supervision of an expert.