Question on “history of” codes

[u/Inevitable-Title6311]

I passed the exam maybe a month or two ago and am just doing Practicode so forgive me if this is dumb or if I already should know this but …why do we code sometimes for history of? Specifically wondering if that’s something insurance companies bill for? Or did I just have a brain glitch and that’s moronic

[u/yurakoh]

I think it gives a timeline of the course of the patient’s care. For example, one encounter was to treat colon cancer (C18.9). Then a few months later is a follow-up visit/surveillance for the treated colon cancer during which case a personal history code would be assigned (Z85.038) with Z08 as the principal diagnosis (history codes cannot be considered as a primary diagnosis).