I would recommend allowing a person to add multiple symptoms up front on the landing page instead of just one. Requiring a postback and then having it to calculate the probabilities under "I may have" after entering only one symptom when the person already knows they plan on entering 2 or 3 more is a waste of resources on the system end as well as a significant delay on the user's end.
That's a fair suggestion. The question is if "rewarding" people with a list of diagnoses from just 1 symptom is worth the cost of resources. My fear is that in the process of having people enter an arbitrary number of symptoms and then having to click a "next" button, they will lose their interest, but we'll test that.
