Performance of a Smartphone-based Stool Test for Use in Colorectal Cancer Screening: Population-based Study

BACKGROUND & AIMS: Noninvasive colorectal cancer (CRC) screening bears high potential for increasing participation if implemented in a straightforward way. We have evaluated the feasibility and diagnostic performance of a smartphone-based fecal immunochemical test (FIT) for CRC screening and compared its performance with a laboratory-based FIT. METHODS: Individuals scheduled for a screening colonoscopy in gastroenterology practices in Southern Germany enrolled into the BLITZ study between 2021 and 2023 were offered a smartphone-based FIT and a laboratory FIT. The smartphone-based FIT consists of a rapid test and a smartphone app. The app quantitatively evaluates the result of the rapid test using the smartphone camera. The feasibility of the smartphone-based FIT was evaluated in a self-administered questionnaire. The comparative performance of the 2 FITs was evaluated by sensitivity, specificity, and receiver-operator curve (ROC) measures. RESULTS: Of 654 study participants who were offered both a smartphone-based FIT in addition to the laboratory FIT, 361 (55%) made use of the smartphone-based FIT, 274 (76%) of those had a valid smartphone-based FIT, and 643 (98%) used the laboratory FIT. Overall, 89% considered the smartphone-based FIT as a useful alternative offer to the laboratory FIT. The reasons why the smartphone-based FIT was not used were mostly technical (app- or smartphone-related, 47%) or reflecting more general concerns or attitudes towards such a test (44%). The smartphone-based FIT showed a sensitivity for advanced neoplasms (28%; 95% confidence interval [CI], 13%-47%) similar to the laboratory FIT (34%; 95% CI, 18%-54%) at an identical specificity (92%; 95% CI, 87%-95%). CONCLUSIONS: The smartphone-based FIT could serve as an alternative in addition to currently offered laboratory FITs. STUDY REGISTRATION: German Clinical Trials Register (drks.de), Number: DRKS00008737.