Defining Medical Necessity
Medical necessity refers to healthcare services or supplies that are reasonable and necessary for the diagnosis or treatment of illness or injury, consistent with accepted standards of medical practice. Medicare and other payers require documented medical necessity as a condition of payment, making it a central Revenue Cycle domain concept for RHIA candidates.
Sources of Medical Necessity Criteria
- National Coverage Determinations (NCDs): Medicare-wide policies specifying whether and under what conditions a service is covered
- Local Coverage Determinations (LCDs): policies issued by regional Medicare Administrative Contractors that apply within their specific jurisdiction, often addressing services not covered by an NCD
- Payer-specific medical policies: commercial payers publish their own coverage criteria, which may differ from Medicare's standards
Advance Beneficiary Notices
When a provider believes Medicare may deny a service as not medically necessary, an Advance Beneficiary Notice of Noncoverage (ABN) should be issued to the patient before the service is rendered, informing them of potential financial responsibility. Without a properly executed ABN, the provider may be prohibited from billing the patient if Medicare denies the claim, shifting financial liability back to the provider.
Documentation Supporting Medical Necessity
Medical necessity must be supported by clinical documentation reflecting the patient's diagnosis, symptoms, and clinical rationale for the ordered service, and this documentation must correspond to the diagnosis codes reported on the claim. A mismatch between the diagnosis code billed and the clinical documentation on file is a leading cause of medical necessity denials during payer audit.
Medical Necessity Denials
Denials for lack of medical necessity typically require an appeal supported by additional clinical documentation demonstrating that coverage criteria were met at the time service was rendered. HIM and clinical documentation improvement staff play a key role in ensuring documentation captures the clinical justification needed to support necessity determinations proactively, reducing downstream denial risk.
Level of Care Considerations
Medical necessity also applies to determining the appropriate level of care, such as inpatient versus observation status, using criteria such as InterQual or MCG guidelines. Incorrect level-of-care determinations can trigger both compliance risk, if inpatient criteria were not met, and revenue risk, if the correct outpatient payment structure was not applied.
Exam Tips
Expect questions distinguishing NCDs from LCDs and questions on when an ABN must be issued to protect provider billing rights. Level of care determination scenarios are also frequently tested.
Key takeaway: Documented medical necessity underlies payer reimbursement decisions, and understanding NCDs, LCDs, and ABN requirements is essential Revenue Cycle domain knowledge.