You are making presumption that every user is familiar with swiping card UI from Tinder. Also, after some poking around and finding how it actually works, there's no way to reset or change your choice - only hard reload.

I would add simple instructions how to use this tool, e.g. "Swipe left for No, left for YES answer". Also do calculation for user, do not show just numbers. Simple if statement at the end of questionnaire should state "Based on {the algorithm} you should consult a doctor immediately". You must emphasize that there is a margin of error.