Whether they are trying to understanding exclusions, co-pays, out-of-pocket expenses, deductibles, authorizations, or referrals, patients often find that navigating their insurance plan can often be a confusing and overwhelming task. Particularly, understanding the difference between preventive services and diagnostic services tends to be the most challenging for patients, according to Ellen Risotti, an AAPC Physician Services member in Indianapolis, Ind., who specializes in billing.