7.1 NCDs, LCDs, and Medical Necessity

Why coverage rules belong on the coder's desk

The AAPC Certified Outpatient Coder exam tests National Coverage Determinations (NCDs), Local Coverage Determinations (LCDs), and Advance Beneficiary Notices of Noncoverage (ABNs) in a three-question Compliance domain. Those items are small in count and large in money. On a hospital outpatient department (HOPD) or ambulatory surgery center (ASC) claim, a perfectly chosen CPT or HCPCS code still fails if Medicare does not consider the service reasonable and necessary for that patient on that date. The coder is the last person who can stop a line that will deny, trigger a Recovery Audit, or leave the facility holding the bill because nobody issued a valid ABN.

Medicare payment is not a clinical courtesy. Under Social Security Act §1862(a)(1)(A), coverage is limited to items and services that are reasonable and necessary for the diagnosis or treatment of an illness or injury (or to improve the functioning of a malformed body member) and that fall inside a Medicare benefit category. Cosmetic surgery that is never a benefit, a screening that has already met its frequency cap, and a CT scan ordered for a diagnosis the coverage article does not list are three different problems. The coder's job is to tell them apart before the UB-04 (HOPD) or CMS-1500 (independent ASC) leaves the department.

National Coverage Determinations

An NCD is national policy from the Centers for Medicare & Medicaid Services (CMS). It grants, limits, or excludes Medicare coverage for a specific item or service in every state. CMS develops NCDs through an evidence-based process with public participation; some reviews also use an outside technology assessment or the Medicare Evidence Development & Coverage Advisory Committee (MEDCAC). The Medicare Coverage Center and the Medicare Coverage Database (MCD) are the public homes for this work. NCDs are published in the Medicare National Coverage Determinations Manual (Pub. 100-03).

CMS's own document-type description is the rule facility coders should memorize: Medicare Administrative Contractors (MACs) are required to follow NCDs. If an NCD does not specifically exclude or limit an indication, or if the item is not mentioned in an NCD or a Medicare manual, the MAC may still cover the service through an LCD. LCDs cannot contradict NCDs. They exist to clarify an NCD or to address common coverage issues when there is no national policy.

Two implementation facts keep showing up on exams and in claim edits:

• CMS must issue a manual transmittal, CMS ruling, or Federal Register notice with an effective date and an implementation date before contractors can operationalize an NCD. The NCD itself becomes effective on the date of the decision memorandum.
• NCDs usually do not contain claims-processing codes. They do not list CPT/HCPCS or ICD-10-CM the way a billing article does. For diagnosis and procedure code instructions, CMS points you to Change Request transmittals, the Medicare Claims Processing Manual, and—especially for laboratory NCDs—the ICD-10 code lists that travel with those national lab policies.

Coding Analyses for Labs (CALs) are a related national process. A CAL updates the diagnosis-code component of a negotiated laboratory NCD when there is a question about whether a code flows from the NCD's narrative indications. That is why a lipid panel or glycosylated hemoglobin claim can deny nationally for the wrong ICD-10-CM even when no LCD exists in your state.

Local Coverage Determinations and coverage articles

An LCD is a MAC decision, for that contractor's jurisdiction, about whether an item or service is reasonable and necessary under §1862(a)(1)(A). Social Security Act §1869(f)(2)(B) and §1862(l)(5)(D) define LCDs and the process. LCD document IDs begin with L (for example, L12345). Proposed LCDs begin with DL. Chapter 13 of the Medicare Program Integrity Manual governs how MACs develop them, including a public comment period on the proposed LCD.

After LCD modernization, codes generally no longer live in the LCD policy text. You find them in Articles. Article IDs begin with A; draft articles begin with DA. CMS describes several article types:

A Billing and Coding Article that supports an LCD is the working document for diagnosis-to-procedure linkage. It tells you which procedure codes the LCD applies to, which diagnoses support medical necessity, and which diagnoses the contractor will treat as not reasonable and necessary. If you search the MCD by CPT/HCPCS and state, the article—not the LCD narrative—is usually where the ICD-10-CM list sits. Durable Medical Equipment MACs are a partial exception: DME still often keeps codes inside the LCD itself.

Diagnosis-to-procedure linkage on HOPD and ASC claims

Medical necessity is not a vague clinical impression. For the claim, it is a documented indication plus a covered code pair:

1. Confirm the service is in a Medicare benefit category (hospital outpatient, ASC covered procedure, diagnostic test, and so on).
2. Search the MCD for an NCD. If one exists, apply its clinical limitations nationwide.
3. If no NCD (or the NCD leaves room), open the LCD for your MAC and the Billing and Coding Article.
4. Assign the first-listed ICD-10-CM diagnosis from the encounter documentation that actually supports that procedure—not a convenient chronic code from the problem list.
5. Watch frequency language. Many NCDs and LCDs pay a service only at stated intervals. A second screening in the same period is a medical-necessity problem even if the CPT code is correct.
6. Distinguish screening from diagnostic work. A screening colonoscopy that becomes a diagnostic procedure because a polyp is removed is not coded, or covered, the same way as a pure screening. The diagnosis must tell that story.

Every service billed must indicate the specific sign, symptom, or complaint that makes it reasonable and necessary. CMS's Medicare Learning Network booklet on advance notices (MLN006266, May 2025) states the operational consequence: once an NCD or LCD is published, the provider knew or should have known that Medicare would deny the service as not medically necessary if the patient does not meet the criteria.

HOPD scenario: CT that the article will not support

A 71-year-old Medicare Fee-for-Service patient presents to the HOPD for a CT abdomen and pelvis with contrast. The order diagnosis is Z00.00 (encounter for general adult medical examination without abnormal findings). The operative or radiology report describes no acute abdominal complaint. Your MAC's Billing and Coding Article for abdominal CT lists covered indications such as abdominal pain, mass, and staging of a known neoplasm. Z00.00 is not on the covered list.

Correct coder action is not to invent a pain code. Correct action is to query if the record actually documents a covered indication. If the record truly supports only a screening or “rule-out” exam without a covered diagnosis, the line is expected to deny as not reasonable and necessary. That is an ABN conversation before the scan—not a HINN, and not a hope that the NCD is silent so the claim will slip through. Silence in an NCD does not mean “always payable”; it means you still need LCD/article support or contractor medical review.

The ABN does not rewrite coverage

Facility staff sometimes think a signed ABN “covers” whatever the NCD noncovers. That is backwards. An NCD that says a service is not reasonable and necessary still leaves the service in a benefit category; Limitation On Liability rules may let a mandatory ABN shift financial risk to the beneficiary if the notice is valid. An item that is statutorily excluded or that is never a Medicare benefit is different. CMS ABN form instructions (CMS-R-131) allow a voluntary notice as a courtesy for never-covered care, but they do not require option boxes or a signature, and they do not make Medicare pay the line as a covered service. The ABN does not override statutory exclusion, and it does not override an NCD that places the item outside coverage as a never-covered benefit. Section 7.3 works the modifiers; the coverage rule belongs here so you do not pick GA when the right story is GY.

Traps that cost hours on the claim

• Treating an LCD as optional because “the NCD is national.” If the NCD is silent, the LCD is how your MAC will review the claim.
• Coding from the LCD prose and skipping the article's ICD-10-CM table.
• Using a history or status Z code as first-listed when the article requires the acute indication.
• Assuming Medicare Advantage (Part C) follows the same NCD/LCD/ABN packet. Original Medicare coverage documents still matter as a floor for many MA plans, but the ABN is a Fee-for-Service notice, not a Part C notice.
• Confusing a national noncoverage NCD (medical necessity) with a statutory exclusion (never a benefit). Only the first is a classic mandatory-ABN medical-necessity problem.