A molecular lab gets two claims denied for the exact same test on the exact same week. One patient lives in North Carolina, the other in Ohio. Same CPT code, same documentation, same clinical story. One denial cites a national rule; the other cites a local one the billing team had never read. Nothing was wrong with the lab. What was wrong was the assumption that Medicare coverage is one thing.
It is not. Medicare coverage runs on two parallel tracks, and a claim has to clear whichever ones apply to it. Understanding the difference between a National Coverage Determination and a Local Coverage Determination is the difference between predicting your denials and being surprised by them.
Disclaimer: This article is educational and is not medical, legal, or billing advice, and it is not a coverage determination for any specific patient or claim. Coverage policies change, contractors interpret them differently, and the only authoritative sources are the current NCD, LCD, and Article language in the CMS Medicare Coverage Database. Always verify against current policy and consult qualified clinical, billing, and compliance professionals before making coverage, billing, or treatment decisions. Use this information at your own risk.
The shared foundation: "reasonable and necessary"
Both kinds of determination answer the same underlying question. Under Section 1862(a)(1)(A) of the Social Security Act, Medicare generally cannot pay for items or services that are not "reasonable and necessary for the diagnosis or treatment of illness or injury." (CMS; SSA §1862) An NCD and an LCD are simply two different mechanisms for deciding what counts as reasonable and necessary, at two different levels of government.
The level matters because it determines who decides, how far the decision reaches, and how the two decisions stack.
NCDs: the national floor
A National Coverage Determination is a coverage policy issued by the Centers for Medicare & Medicaid Services (CMS) that sets, on a nationwide basis, the extent to which Medicare will cover a specific item, service, or technology. (CMS) An NCD is the closest thing Medicare has to a single national answer.
Two features make NCDs powerful. First, they are binding on all Medicare contractors and entities; under Section 1869(f) of the Social Security Act, NCDs bind the contractors that process claims, and administrative law judges may not disregard them. (CMS transmittal; SSA §1869) Second, they are slow and deliberate to make or change. For a request that does not require an external technology assessment or advisory committee review, CMS must issue a proposed decision within 6 months; requests that do require that review get 9 months. A proposed decision then posts for a 30-day public comment period, with the final decision due within 60 days after comments close. (CMS) An NCD is a major, infrequent event.
For molecular labs, NCD 90.2 (next-generation sequencing for cancer) is the textbook example of a national rule that sets the floor for a whole category of testing.
LCDs: local detail where the national rule stops
A Local Coverage Determination is a decision by a Medicare Administrative Contractor (MAC) about whether a particular item or service is reasonable and necessary, and therefore covered, within that contractor's jurisdiction only. (CMS) MACs are the private companies CMS contracts with to administer Medicare claims region by region; each one covers a defined set of states.
Crucially, MACs develop an LCD when there is no NCD on the topic, or when an existing NCD needs to be further defined for the local jurisdiction. (CMS) That is the heart of the relationship. LCDs fill gaps and add specificity; they do not override the national layer. The Medicare Program Integrity Manual is explicit that LCDs must not conflict with statutes, regulations, CMS rulings, or national coverage policy. (CMS PIM Ch. 13)
LCDs also move on their own clock. A proposed LCD must be published on the Medicare Coverage Database and open for public comment for a minimum of 45 days, with an open meeting during that window; the final LCD then carries a notice period of at least 45 days before it takes effect. (CMS PIM Ch. 13; Epstein Becker Green) Because every MAC runs that process independently, the same test can gain, lose, or change coverage in one jurisdiction while staying untouched in another.
LCD vs. NCD at a glance
| Dimension | NCD (National Coverage Determination) | LCD (Local Coverage Determination) |
|---|---|---|
| Who issues it | CMS | A Medicare Administrative Contractor (MAC) |
| Geographic scope | All of Medicare, nationwide | Only the issuing MAC's jurisdiction(s) |
| What it governs | Whether an item/service is reasonable and necessary, set as a national policy | Whether an item/service is reasonable and necessary within that jurisdiction; often adds local detail where no NCD exists |
| Precedence / relationship | Binding on all contractors; LCDs cannot conflict with it | Must stay consistent with NCDs, statutes, and regulations; operates in the space an NCD leaves open |
| How it's found | CMS Medicare Coverage Database (national coverage updated in real time) | CMS Medicare Coverage Database (local coverage captured weekly, displayed the following Thursday) |
| How often it changes | Infrequent; formal multi-month process with a 30-day comment period | More frequent and varies by MAC; minimum 45-day comment period plus a 45-day notice period |
Sources for the table values are listed in the Sources section below. (CMS coverage process; CMS local; MCD intro; CMS PIM Ch. 13)
How they interact on a real claim
The cleanest way to think about it: the NCD is the national floor, and the LCD is the local detail built on top of it where the floor allows. A claim has to clear every determination that applies to it.
Three common situations follow from that:
- An NCD exists and settles the question. The national rule controls, and any LCD in the picture has to be consistent with it. Here, knowing the NCD is most of the work.
- No NCD exists. The MAC's LCD (and its companion coding Article) is the operative policy, and it can differ from one jurisdiction to the next. Two labs running the identical test can face different rules purely because of where the patient's claim is adjudicated.
- An NCD exists but leaves room. Some NCDs explicitly defer parts of the coverage decision to the contractors. The NCD sets the frame; the LCD fills in local specifics like covered indications, documentation expectations, and coding. NCD 90.2 works this way for many non-FDA-approved tests, which is exactly why MolDX policy carries so much weight in molecular diagnostics.
One subtlety worth flagging: the coding and billing instructions you actually need to get a claim right often live not in the LCD itself but in an associated Article. CMS guidance directs that coding guidelines are not part of the LCD and should be published in Articles instead. (CMS PIM Ch. 13) Reading the LCD without its Article is a frequent way teams miss the requirement that denies them.
Why this distinction decides molecular and diagnostic payment
For diagnostic, genetic-testing, and specialty labs, the LCD layer is where most coverage action happens, because so many molecular tests have no dedicated NCD. That is the gap the MolDX program was built to fill. MolDX was developed by Palmetto GBA to set coverage and reimbursement standards for molecular diagnostic tests, and several other MACs, including Noridian, WPS, and CGS, have adopted MolDX policies in their own jurisdictions. (CMS LCD L35025; Palmetto GBA) The practical result is that whether your test is covered, and under what conditions, frequently turns on which MAC adjudicates the claim and what that MAC's current MolDX LCD and Article say.
This is where the two tracks become an operational problem rather than a trivia question. A national rule can stay frozen for years while a relevant MolDX LCD is revised, retired, or replaced on a 45-day cycle in one jurisdiction and not another. Your coverage picture for a single test is the sum of an NCD that changes rarely and a set of LCDs that change independently, on different calendars, in different regions. Tracking only the national layer, or only your "home" MAC, leaves blind spots that show up as denials.
That per-jurisdiction coverage logic, every applicable NCD plus the relevant local LCD and Article, on their own changing schedules, is exactly what Converus monitors so labs can see where a given test is payable and what each jurisdiction currently requires, rather than discovering it one denial at a time.
The takeaway
NCDs and LCDs are not competing answers to the same question; they are two layers of one system. The NCD sets a binding national floor. The LCD, written by a MAC, adds local detail where the national rule is silent or deferential, and it can never conflict with the national rule above it. To get paid, a claim must satisfy whichever determinations apply, national and local, and those determinations change on independent schedules. For molecular and diagnostic labs especially, the local layer is often the one that actually decides the claim, which is why "Is it covered by Medicare?" is rarely a single national yes or no.
Sources
- CMS, Medicare Coverage Determination Process — https://www.cms.gov/medicare/coverage/determination-process
- CMS, Local Coverage Determinations — https://www.cms.gov/medicare/coverage/determination-process/local
- CMS, Pub. 100-03 Medicare National Coverage Determinations (transmittal, NCD binding effect) — https://www.cms.gov/regulations-and-guidance/guidance/transmittals/downloads/r59ncd.pdf
- CMS, Medicare Program Integrity Manual, Chapter 13 — Local Coverage Determinations (LCD/NCD consistency, comment and notice periods, Articles) — https://www.cms.gov/regulations-and-guidance/guidance/manuals/downloads/pim83c13.pdf
- CMS, How to Use the Medicare Coverage Database — Introduction (document types; update timing) — https://www.cms.gov/Outreach-and-Education/MLN/Educational-Tools/MLN901347-How-to-MCD/mcd/mcd/chapter_1_introduction/
- Social Security Act §1862 (reasonable and necessary) — https://www.ssa.gov/OP_Home/ssact/title18/1862.htm
- Social Security Act §1869 (NCD binding effect, review limits) — https://www.ssa.gov/OP_Home/ssact/title18/1869.htm
- CMS Medicare Coverage Database, LCD — MolDX: Molecular Diagnostic Tests (L35025) — https://www.cms.gov/medicare-coverage-database/view/lcd.aspx?lcdid=35025
- Palmetto GBA, MolDX Frequently Asked Questions — https://palmettogba.com/palmetto/moldxv2.nsf/DID/9A7MFG4181
- Epstein Becker Green, CMS's New Process for Issuing Local Coverage Determinations (45-day comment and notice periods) — https://www.ebglaw.com/insights/publications/cmss-new-process-for-issuing-local-coverage-determinations