Compliance and Reimbursement
From documentation to dollars
Inpatient payment under IPPS uses the MS-DRG, assigned from the principal diagnosis, secondary diagnoses (CC/MCC), procedures, discharge disposition, and for some DRGs age and sex. Outpatient payment under OPPS uses APCs. Physician services use the MPFS: RVUs (work, practice expense, malpractice) × GPCI × conversion factor. Critical access hospitals are largely cost-based; SNFs and home health use their own prospective models; value-based programs adjust payment for quality, readmissions, and hospital-acquired conditions.
Medical necessity is the overarching requirement: services must be reasonable and necessary and supported in the documentation. NCCI edits (procedure-to-procedure and medically unlikely edits) prevent unbundling and inappropriate units. A correct modifier (-25 for a significant, separately identifiable E/M; -59 or the X{E,S,P,U} modifiers for distinct services) can bypass an edit only when the documentation supports it. MACs, RACs, and other auditors recover overpayments; the OIG Work Plan sets audit priorities.
Fraud is intentional deception; abuse is conduct inconsistent with sound fiscal, business, or medical practice and may be unintentional. CDI programs use concurrent review and non-leading physician queries to clarify documentation that affects severity, DRG assignment, and quality metrics; the physician always makes the final decision, and the query response becomes part of the record.
Worked example: an E/M visit and a minor procedure on the same day trigger a PTP edit. Append modifier -25 to the E/M only if the note shows significant, separately identifiable work beyond the procedure's usual pre- and postoperative care. If the note only says 'evaluated and treated the lesion,' no -25 is supported.
Traps: assuming a modifier overrides an edit regardless of documentation; equating a higher CMI with better compliance; mixing up fraud and abuse; forgetting that ABNs apply to statutorily excluded services.