Pharmacogenetic (PGx) testing, also called pharmacogenomic testing, looks at genes that affect how a patient processes certain medications. The results can change which drug a clinician prescribes or what dose they start with. Payers will pay for that when the test is tied to a specific drug decision. They usually won’t pay for broad panels ordered just in case, and that distinction drives most PGx denials.
PGx claims are billed by the laboratory that performs the test, not by the practice that orders it. The lab needs the right gene-specific codes, a registered test identifier for Medicare, and documentation from the ordering clinician showing which medication decision the test supports.
Key Takeaways
- PGx tests bill under gene-specific codes such as 81225 (CYP2C19), 81226 (CYP2D6), and 81227 (CYP2C9), or under a panel or PLA code when one applies.
- Medicare covers PGx testing through MolDX when the result is needed to select or dose a specific drug, and the test has to be registered with a Z-code identifier.
- Preemptive panels for patients with no current drug decision are generally not covered.
- The performing lab bills the test. The ordering practice doesn’t bill for the test or for collecting a cheek swab.
- PGx labs need a CLIA certificate for high-complexity testing and, in some states, a state lab license.
PGx CPT Codes
Most PGx testing bills under Tier 1 molecular pathology codes, each tied to a single gene. When a lab tests several genes for one drug decision, it bills the code for each gene that was clinically needed. Some labs offer proprietary PGx tests with their own PLA codes, and when a test has a PLA code the lab has to use it.
- 81225 (CYP2C19, used for clopidogrel and many antidepressants)
- 81226 (CYP2D6, used for codeine, tramadol, tamoxifen, and many psychiatric drugs)
- 81227 (CYP2C9, used for warfarin and some NSAIDs)
- 81355 (VKORC1, used for warfarin)
- 81232 (DPYD, used for fluorouracil and capecitabine)
- 81335 (TPMT, used for thiopurines)
- 81306 (NUDT15, used for thiopurines)
- 81230 and 81231 (CYP3A4 and CYP3A5, used for tacrolimus)
Billing a panel of genes when only one or two were relevant to the medication in question is the most common reason PGx claims are cut back or denied. Our guide to which CPT codes are used in PGx testing billing covers the full code list.
Medicare Coverage and MolDX
Most Medicare contractors handle PGx through the MolDX program. MolDX covers PGx testing when the patient is being considered for a drug with a known gene-drug interaction, the result will be used to choose the drug or set the dose, and the test hasn’t already been done. Gene-drug pairs supported by FDA labeling or CPIC guidelines are the strongest basis for coverage.
Each test has to be registered in the DEX Diagnostics Exchange, and its Z-code identifier goes on every Medicare claim. A claim without it denies. Testing for warfarin response is handled differently, under a national coverage policy that limits payment, so warfarin genotyping should be checked before it’s ordered for a Medicare patient.
When a test may not meet coverage criteria, the lab should obtain a signed Advance Beneficiary Notice before running it and bill with the GA modifier. Without a valid ABN, the patient can’t be billed for a denied test.
Diagnosis Codes and Documentation
The diagnosis on a PGx claim should be the condition being treated, such as major depressive disorder, atrial fibrillation, or a cancer diagnosis, because that’s what ties the test to a drug decision. Codes for long-term drug therapy (Z79 codes) can support the claim when the patient is already on the medication. A screening code alone rarely supports coverage.
The ordering clinician’s note does most of the work. It should name the drug being considered or adjusted, explain why genotype matters for that drug, and state how the result will change prescribing. Labs should request this documentation with the order, since payers ask for it on review and appeal.
Prior Authorization and Commercial Coverage
Commercial plans vary widely. Some cover single-gene tests tied to a specific drug and deny multigene panels, while others send all genetic testing through a lab benefit manager with its own criteria. Prior authorization is common, and the request needs the drug, the clinical reason, and the specific codes.
The approval has to match the claim. If the authorization covers one gene and the lab bills several, the extra codes deny, which we cover in why an approved authorization can still end in a denied claim. Denied claims can be appealed with the ordering note and the published guideline for that gene-drug pair.
PGx Lab Credentialing
PGx testing is high-complexity testing, so the lab needs a CLIA Certificate of Compliance or Certificate of Accreditation. Several states, including New York, require out-of-state labs to hold a state license before testing specimens from residents. Independent labs enroll with Medicare as a facility through the CMS-855B and bill the Medicare contractor for the state where testing is performed.
Commercial and Medicaid plans contract with labs separately, and many PGx claims go out of network until those contracts are in place. Our credentialing team handles CLIA documentation, state licenses, and payer enrollment together. Labs that also run broader molecular testing can see our genetic testing page.
PGx Billing FAQs
Which CPT code is used for CYP2D6 testing?
CPT 81226. CYP2C19 is 81225, and CYP2C9 is 81227. Each gene tested bills under its own code unless the test has a PLA code.
Does Medicare cover pharmacogenetic testing?
Yes, through MolDX, when the result is needed to select or dose a specific drug with a known gene-drug interaction. Preemptive testing without a current drug decision is generally not covered.
Who bills for a PGx test?
The laboratory that performs the test. The ordering practice doesn’t bill for the test, and collecting a cheek swab isn’t separately billable.
What diagnosis code should be used on a PGx claim?
The condition being treated with the medication in question. Long-term drug therapy codes can support it, but a screening code alone rarely supports coverage.
Why are PGx panels denied?
Most payers cover only the genes relevant to the drug decision. A panel that includes genes with no current clinical use is usually denied or reduced.
What does a PGx lab need for credentialing?
A CLIA certificate for high-complexity testing, state licenses where required, Medicare enrollment through the CMS-855B, and contracts with each commercial and Medicaid plan.
Medwave and PGx Labs
PGx claims are judged on medical necessity, and most denials say the test wasn’t tied to a drug decision. Medwave checks that the order names the medication being considered, that the test is registered where MolDX requires it, and that panel codes match what was run. Our billing team clears 98% of PGx claims on first submission.
Labs need CLIA, state licenses, and payer enrollment in place before testing. Our credentialing team handles all of it, averaging 85 days for enrollment, and our payer contracting team works on coverage with plans that still exclude PGx panels.
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