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* = Presenting author

P273 Validation of a smartphone-based patient monitoring system measuring Calprotectin as the therapy follow-up marker

J. Weber*1, M.-E. Ueberschlag1, M. Prica1, S. Kräuchi1, C. Reinhard2, T. Jermann1

1BÜHLMANN Laboratories AG, R&D, Schoenenbuch, Switzerland, 2BÜHLMANN Laboratories AG, Operations, Schoenenbuch, Switzerland

Background

Inflammatory Bowel Disease (IBD) is a chronic inflammation of the gut comprising active inflammation, remission and flares. The disease course can be followed by biomarkers such as calprotectin which is measured in patients' stool samples. Most studies have shown that a threshold around 250 µg/g correlates well with mucosal healing. Hence, one of the therapy goals is to achieve calprotectin values below 250 µg/g. We have developed a system, called IBDoc®, which allows the patient to perform calprotectin tests at home. The IBDoc® consists of a stool extraction device (CALEX® Valve) and an immunochromatographic rapid test, which is measured by a smartphone App (CalApp®) controlling the phone's camera. Results are automatically sent to a webserver (IBDoc® Portal).

The objective of this study was to validate the IBDoc® home testing system and to compare its performance with laboratory-based stool extraction and Calprotectin ELISA Methods.

Methods

A multitude of leftover stool samples, kindly provided by a local routine clinical laboratory, were extracted with the CALEX® Valve device and by conventional laboratory Methods. The stool extracts were then either loaded onto immunochromatograhic test cassettes or analyzed with a commercial ELISA test. The test cassettes were read via the CalApp® installed on different iPhones and Android phones, whereas the ELISA was performed in a spectrophotometer. All common technical performance characteristics of the IBDoc® system were determined, and the quantitative IBDoc® Results were compared to the Results obtained by the laboratory-based ELISA method.

Results

The IBDoc® test system produces a quantitative test result between 30 and 1000 µg of calprotectin/g of stool which covers the clinically relevant range of this biomarker. Smartphone model specific calibration parameters were established to correct the measured raw data for differences in camera optics and image processing resulting in correct and equal test Results among a broad range of smartphone models. Measuring the same test cassette 20-times resulted in CVs of 3-6%, while measuring the same stool extract on 20 different cassettes gave CVs of 10-20%. The total imprecision considering variations in stool extraction, test cassette runs and smartphone readouts is in the range of 25% CV. The IBDoc® home test correlates well with a state-of-the-art laboratory-based ELISA method showing a bias of < 20% and R2 of >0.85.

Conclusion

IBDoc® is the first complete and validated test system which allows the IBD patient to monitor and follow his inflammatory status by measuring the IBD biomarker, fecal calprotectin, using his own smartphone. The performance of the IBDoc® home testing system is comparable to professional, laboratory-based Methods.