P625 Head-to-head comparison of three stool calprotectin tests for home use
S-M. Haisma*1, A. Galaurchi2, S. Almahwzi2, J. Adekanmi Balogun2, A. Muller Kobold3, P. van Rheenen1
1University Medical Center Groningen, Paediatric Gastroenterology, Groningen, The Netherlands, 2University Medical Center Groningen, Groningen, The Netherlands, 3University Medical Center Groningen, Laboratory Medicine, Groningen, The Netherlands
Calprotectin-guided disease monitoring is done by periodically testing stool samples with an enzyme-linked immunosorbent assay (ELISA). Several manufacturers introduced a lateral flow–based test with software application that turns a smartphone camera into a reader for quantitative measurements. We compared three home tests (IBDoc, QuantonCal and CalproSmart) and companion ELISA tests (fCAL, IDK-Calprotectin and Calprotectin-ALP) to see if measurement pairs agreed sufficiently.
Method comparison study with 40 homogenised stool samples from patients with active or quiescent inflammatory bowel disease. Home tests were done with two iOS (iPhone 6 and 7) and two Android devices (Samsung Galaxy S6 and Motorola Moto G5 Plus). Primary outcome was test agreement (defined as percentage of paired measurements within predefined limits of difference). Secondary outcome included reading error rate (RER) per smartphone type.
We performed 1440 smartphone readings and 120 ELISA tests. In the low calprotectin range ( ≤500 μg/g) IBDoc, QuantOnCal and CalproSmart showed 87%, 82%, and 76% agreement with their companion ELISAs. In the high range (>500 μg/g) the agreement was 37%, 19% and 37%, respectively. CalproSmart and QuantOnCal had significantly higher RERs than IBDoc (respectively, 5.8% and 4.8%, vs. 1.9%). Forty-three per cent of reading errors was on the Motorola device, in particular with the QuantOnCal application.
All three calprotectin home tests and companion ELISAs agreed sufficiently when concentrations are ≤500 μg/g. We recommend to always use the home test and ELISA of one and the same manufacturer. Manufacturers should explicitly evaluate and report the suitability of commonly used smartphones for quantitative calprotectin readings.