Actually there are no guidelines that I've ever seen that state that an HPI must be documented; the guidelines say that in order to code a new patient, consult, initial hospital visit (i.e any E&M that requires 3/3 key components) you must have an HPI documented.
There must be a chief complaint, though.
So if you are coding an E&M with no HPI, but you have an exam and MDM, you technically have the criteria for an established patient OV, or a subsequent hospital visit.
Of course, we'd love for all of our providers to document a clear, concise and legible SOAP note, but we have to work with what we get. This is where an EMR is helpful; our particular software will alert the provider if they forget to document any one of the key components. Otherwise, we continue to provide education to our docs and remind them to document a complete note!
However, if you do find CMS or AMA guidelines somewhere that indicate that an HPI is mandatory, can you please post the link? Thanks, Pam