Genetic Testing Updated June 19, 2026

Liquid Biopsy and ctDNA Reimbursement: How Medicare Covers (and Denies) Plasma-Based Genomic Profiling

FDA-approved companion-diagnostic liquid biopsies have a defined Medicare pathway, while screening and many early-stage uses remain investigational. Coverage turns on the test, the indication, and the patient's stage.

Liquid Biopsy and ctDNA Reimbursement: How Medicare Covers (and Denies) Plasma-Based Genomic Profiling

A metastatic lung cancer patient walks into your affiliated clinic on a Friday. The oncologist needs a genomic answer fast, the tissue block is thin, and a re-biopsy means another procedure and another two weeks. So the physician orders a blood draw instead. The liquid biopsy comes back in days, names an actionable alteration, and the patient starts targeted therapy. Clinically, this is a win. Then the claim posts, and it denies.

If you run a lab, an oncology practice, or a revenue-cycle function, you have lived some version of that story. Liquid biopsy is one of the fastest-moving categories in molecular oncology, and the gap between "clinically appropriate" and "reimbursed" is wide and shifting. The good news: there is real, durable Medicare coverage here. The catch: it is conditional, test-specific, and indication-specific, and the conditions change as the FDA approves new companion-diagnostic claims and Medicare contractors revise their policies. Getting paid depends less on whether liquid biopsy is "covered" in the abstract and more on whether this assay, for this patient's cancer and stage, lines up with a current policy.

Educational disclaimer. This article is for general educational purposes only. It is not medical, legal, billing, or reimbursement advice, and it does not guarantee coverage or payment. Coverage policies, codes, and criteria change frequently and vary by payer, contractor, and date of service. Statements here reflect sourced information as of the dates cited; always verify against the current policy and consult qualified professionals before making clinical, coding, or billing decisions. Use at your own risk.

The line that decides everything: companion diagnostic vs. everything else

The single most useful mental model for liquid biopsy reimbursement is a fork in the road. On one side sit FDA-approved companion-diagnostic (CDx) liquid assays used on-label. On the other side sit broader, earlier-stage, monitoring, and screening uses. The two sides have very different coverage stories.

Start with the favorable side. Two plasma-based comprehensive genomic profiling tests anchor the FDA-approved companion-diagnostic category. Guardant360 CDx was the first FDA-approved liquid biopsy for comprehensive genomic profiling, analyzing circulating tumor DNA (ctDNA) from a blood draw, and it carries multiple companion-diagnostic indications across tumor types including lung and colorectal cancer (Guardant Health). FoundationOne Liquid CDx is an FDA-approved next-generation sequencing (NGS) test that analyzes circulating cell-free DNA from plasma in patients with advanced cancer, with multiple companion-diagnostic claims across biomarkers and therapies (Foundation Medicine; FDA).

Why does that FDA status matter so much for Medicare? Because of a national policy hook. Under the National Coverage Determination for Next Generation Sequencing (NCD 90.2), Medicare covers diagnostic NGS lab tests for patients with advanced cancer (recurrent, relapsed, refractory, metastatic, or stage III/IV) when the test has FDA approval or clearance as a companion in vitro diagnostic, has an FDA-approved or cleared indication for use in that patient's cancer, and is ordered by a treating physician with results returned for patient management (CMS NCD 90.2). CMS has stated that tests gaining FDA approval or clearance as an in vitro companion diagnostic automatically receive coverage under the NCD when the other criteria are met (CMS).

That is the cleanest pathway in this whole landscape. An FDA-approved CDx, used on-label, in a patient with advanced disease, ordered appropriately, in a CLIA-certified lab. When all of those align, the coverage question is largely answered at the national level. The operational discipline is making sure every one of those elements is actually true and documented for the claim in front of you, because the denial-prone failures are subtle: the assay was run for an indication outside its on-label CDx claim, or the patient's documented stage does not meet the "advanced cancer" definition.

MolDX and the plasma-based genomic profiling framework

National policy is only half the picture. Most molecular lab claims route through a Medicare Administrative Contractor (MAC), and for molecular diagnostics that usually means the MolDX program run by Palmetto GBA and adopted by several MACs.

MolDX maintains a Local Coverage Determination specifically for plasma-based genomic profiling in solid tumors (CMS LCD L38043; related billing article A57867). This is the framework that governs whether a liquid biopsy is covered as a limited-coverage benefit and under what conditions. Per the policy, patients can be eligible when they are candidates for treatment with a drug that is FDA-approved for their cancer or carries an NCCN category 1 or 2A recommendation tied to a biomarker the assay tests, and when tissue-based comprehensive genomic profiling is infeasible or has not revealed actionable mutations (CMS LCD L38043). The policy also contemplates that other liquid biopsies can be covered for the same indications if they demonstrate comparable performance to the established assay in their intended-use applications.

Two practical points fall out of this. First, the framework is explicitly therapy-linked: coverage flows from whether the result can guide an approved or guideline-supported treatment, not from genomic curiosity. Second, MolDX coverage is not automatic for every plasma test; a new assay typically has to establish its analytical and clinical validity and complete the MolDX technical assessment to qualify. NeoGenomics' PanTracer LBx, for example, was reported to qualify for Medicare coverage under the MolDX plasma-based profiling policy (Clinical Lab Products). The lesson for operators bringing a test to market, or relying on a sendout: coverage is earned per assay, and the MolDX Z-code and billing-article details matter as much as the clinical story.

Note also that MACs have latitude. The local-coverage section of NCD 90.2 expands MAC discretion, including for germline NGS testing across cancer diagnoses (Epstein Becker Green). MACs may cover beyond the NCD's national floor but cannot contradict it. So two patients with identical clinical pictures can land differently depending on jurisdiction and the policy in force on the date of service.

Tissue or blood? The clinical decision shapes the claim

Liquid biopsy did not replace tissue; it joined it, and the coverage logic reflects that. In advanced non-small cell lung cancer, ctDNA testing has shown high concordance with tissue for guideline-recommended biomarkers and a markedly faster turnaround (PMC). That speed is the clinical case for blood-first or concurrent testing. But concordance is not identity. Studies show that when a plasma result is negative and the ctDNA tumor fraction is low, reflexing to tissue can surface previously unidentified alterations in a substantial share of cases (ScienceDirect), and complementary ctDNA testing can add information in many patients while still missing some alterations detectable on tissue (PMC).

Why does a clinical nuance belong in a reimbursement article? Because the MolDX plasma framework bakes the tissue relationship into coverage. The policy's eligibility language leans on whether tissue profiling is infeasible or uninformative, and it points clinicians toward tissue genotyping when no alteration is detected in plasma or ctDNA is insufficient. In other words, the documentation that supports medical necessity is the same documentation that records the clinical reasoning: insufficient tissue, prior tissue testing without actionable findings, the need for a rapid result to start therapy. A liquid biopsy ordered without that rationale in the record is not just clinically thinner; it is a weaker claim. Build the chart so the "why blood" answer is explicit, and the coverage case largely writes itself.

The investigational side of the fork: screening and (still-maturing) monitoring

Now the other side of the road, where enthusiasm has outrun coverage.

Multi-cancer early detection (MCED). Blood tests that aim to screen asymptomatic people for many cancers at once are scientifically exciting and, for Medicare reimbursement purposes, largely not there yet. As of 2026, no MCED test is FDA-approved, and these tests are not routinely covered by Medicare; one prominent test is available through CLIA pathways and marketed without payer coverage (Prevent Cancer Foundation). CMS and the FDA approved an Investigational Device Exemption study enrolling roughly 50,000 Medicare beneficiaries to evaluate clinical impact (GRAIL). Congress has moved as well: the Nancy Gardner Sewell Medicare Multi-Cancer Early Detection Screening Coverage Act was signed into law in February 2026, creating a benefit-category mechanism so Medicare could cover such tests once FDA-approved (AJMC). That is a runway, not a coverage decision. Treat MCED as a watch-this-space category, not a billable line today.

Molecular residual disease (MRD). ctDNA-based MRD testing, detecting trace tumor DNA after treatment to flag recurrence early, sits in a middle zone that has been moving toward coverage. MolDX maintains an LCD for minimal/molecular residual disease testing for cancer (CMS LCD L38835; billing article A58456), and specific assays have qualified for coverage in defined settings. Exact Sciences' Oncodetect, for instance, was reported to receive Medicare coverage through MolDX for serial use in stage II–III and resectable stage IV colorectal cancer in adjuvant and recurrence-monitoring settings (Exact Sciences). The pattern mirrors plasma CGP: coverage is assay-specific and indication-specific, often limited to particular tumor types, stages, and serial-testing schedules. Do not assume MRD coverage in one cancer extends to another.

Why clean-looking claims still deny, and what to do about it

Put the pieces together and a denial taxonomy emerges. Liquid biopsy claims most often fail not because the science is weak but because of an alignment problem between the test as run and the policy as written:

  • Indication mismatch. The assay was used outside an FDA-approved on-label companion-diagnostic claim, or for a cancer type the policy does not cover.
  • Stage mismatch. The patient's documented stage does not meet the "advanced cancer" definition under NCD 90.2, or the early-stage use is not within MAC discretion.
  • Documentation gaps. The record does not establish medical necessity, treating-physician order, or the clinical rationale for plasma over tissue.
  • Stale policy. The claim relied on a coverage understanding that has since changed because the FDA added or modified a CDx claim, or a MAC revised its LCD or billing article.
  • Coding precision. The proprietary laboratory analysis (PLA) code billed must correctly identify the specific assay (these tests are reported with test-specific PLA codes), and pricing for such codes is frequently contractor-priced rather than nationally set (CMS CLFS test code list). Reference CPT and PLA codes by number against current AMA and CMS sources rather than from memory.

The throughline across every one of these failure modes is currency. The covered indication for a given liquid biopsy is not a fixed fact; it is a moving target that updates each time the FDA approves a new companion-diagnostic claim, a MAC posts a revised LCD, or a billing article changes its covered code list. A test that was investigational last year can become covered this year for a specific indication, and a policy can narrow as well as expand. Labs and practices that treat coverage rules as a one-time setup and revisit them only when denials spike are, structurally, always slightly behind the policy.

The operating discipline this category demands

If there is one durable takeaway for a lab director, clinic owner, or revenue-cycle leader, it is this: in liquid biopsy, getting paid is a function of keeping payer coverage rules current per test and per indication. The clinical value of ctDNA is no longer the question. The operational question is whether your order sets, medical-necessity documentation, coding, and payer-policy references reflect what each MAC and commercial plan actually covers today for the specific assay and the specific patient population you serve.

That is precisely the work that is easy to under-resource and expensive to neglect. It means tracking NCD 90.2's national floor, the MolDX plasma-CGP and MRD LCDs and their billing articles, the FDA's evolving list of companion-diagnostic claims, and the commercial medical policies that often lag or diverge from Medicare. It means knowing when a sendout assay has cleared MolDX technical assessment and what indications it is covered for. This is the category Converus works in: keeping reimbursement intelligence current across tests and indications so that coverage rules are tracked deliberately rather than discovered at the remittance. However you resource it, the principle holds. Coverage in liquid biopsy is real but conditional, and the conditions move. Make tracking them a standing process, not an afterthought.

Sources

Frequently Asked Questions

Does Medicare cover liquid biopsy ctDNA testing in oncology?
Medicare can cover plasma-based comprehensive genomic profiling for patients with advanced cancer when criteria are met. FDA-approved companion diagnostics used on-label for the patient's cancer connect to the national NGS pathway (NCD 90.2), and MolDX maintains a Local Coverage Determination for plasma-based genomic profiling in solid tumors. Coverage depends on the specific test, indication, and stage; verify current policy.
What is the difference between a companion-diagnostic liquid biopsy and a screening liquid biopsy for coverage?
FDA-approved companion diagnostics such as Guardant360 CDx and FoundationOne Liquid CDx have a clearer Medicare pathway when used on-label in advanced cancer. Multi-cancer early detection (screening) blood tests are not FDA-approved or routinely covered by Medicare and are generally considered investigational as of 2026.
Is ctDNA-based minimal residual disease (MRD) testing covered by Medicare?
MolDX maintains a Local Coverage Determination for molecular residual disease testing, and specific assays have qualified for coverage in defined indications such as colorectal cancer surveillance. Coverage is test-specific and indication-specific; confirm the current LCD and billing article before relying on it.
Why do clean liquid biopsy claims still get denied?
Denials commonly stem from a mismatch between the test's covered indication and the patient's documented stage or cancer type, use outside an FDA-approved on-label companion-diagnostic claim, missing medical-necessity documentation, or reliance on a coverage policy that has since changed. The covered indication for a given assay can shift as the FDA approves new claims and MACs update LCDs.
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