Validity of a Toilet Seat for Automated Classification of Stool Form Using Falling Stool Sensing

Objective Monitoring the condition of stool is useful for daily health management and early detection of diseases; however, a self-assessment of stool form is often inaccurate. To address this issue, TOTO, developed a prototype toilet seat equipped with a sensor that classifies stool forms according to the Bristol Stool Form Scale (BSFS). This study aimed to verify the accuracy of this method for distinguishing stool types. Methods We recruited 38 healthy Japanese participants and obtained BSFS data using the device from November 2021 to March 2022. Meanwhile, we taught the participants how to assess their own stool using the BSFS and used their assessments as reference standards. We evaluated the strength of agreement between the participants' assessments and the device's classification results using the kappa coefficient, as well as the strength of correlation using Spearman's rank correlation coefficient. Materials We analyzed 305 samples from 38 participants after excluding 62 samples for which the participant's judgment was unreliable or the device data were of a low quality. Results The kappa coefficient between participants' assessments and the device's classification results based on BSFS was 0.55 [95% confidence interval (CI) 0.45-0.65, p<0.001], while the Spearman's rank correlation coefficient was 0.56 (95% CI 0.48-0.63, p<0.001). Conclusion The device appeared to possess limited but moderate validity, with fair to good agreement and moderate correlation with the participants' assessment results. This toilet seat with an automated classification of stool form by sensing falling stool may support daily healthcare and early disease detection.