CPT code 86301 – CA 19-9 tumor marker immunoassay

Key takeaways

CPT 86301 covers the quantitative CA 19-9 serum immunoassay only. CA 15-3 (86300), CA-125 (86304) and CEA (82378) each have their own code.

Medicare covers CA 19-9 under NCD 190.30 to follow patients with established pancreatic or biliary ductal carcinoma, not to screen or work up symptoms.

The core covered pairings are C25.x, C24.x, C22.1 (intrahepatic bile duct carcinoma) and Z85.07 for a history of pancreatic cancer.

Hepatocellular, colorectal and gastric cancer codes fall outside the NCD, so treat them as payer-specific and issue an ABN for Medicare patients.

Pabau’s claims management software builds CMS-1500 claims from invoices, submits them through Claim.MD and tracks each claim to payment or denial.

CPT code 86301: official descriptor and code specifications

CPT code 86301 is the American Medical Association (AMA) code for a quantitative immunoassay for the tumor antigen CA 19-9. CA 19-9 is also called carbohydrate antigen 19-9 or sialyl-Lewis antigen. The test measures serum CA 19-9 in Units/mL, and the clinical or reference laboratory that runs it bills the code.

Medicare also covers it under NCD 190.30 to follow patients with established pancreatic or biliary ductal carcinoma, and pays $20.81 for it in 2026.

Specifically, the code covers only the quantitative serum CA 19-9 measurement. Qualitative tests and urine-based assays, for example, don’t fall under 86301. Nor does CA 19-9 run inside a reflexed panel without a separate order.

Clinical indications: when is CA 19-9 testing medically necessary?

Under NCD 190.30, CA 19-9 testing is medically necessary to follow a patient with an established pancreatic or biliary ductal carcinoma. However, CA 19-9 can’t confirm or rule out cancer on its own. As a result, Medicare doesn’t cover it for patients evaluated for signs or symptoms suggestive of malignancy, or as a screen.

Within that diagnosis, the NCD supports these uses:

• Monitoring response to chemotherapy, radiation or other treatment, including across later treatment cycles
• Assessing whether residual tumor remains after surgery
• Checking for recurrent disease during follow-up, as often as the clinical picture requires

However, hepatocellular carcinoma, colorectal cancer and gastric cancer fall outside the NCD. Some commercial payers cover CA 19-9 for them under their own policies, so check before treating those indications as covered.

Benign pancreatitis, cholestasis, cirrhosis and other non-malignant conditions don’t support medical necessity, even though CA 19-9 often rises in them. A claim with only a pancreatitis code is denied even if the ordering provider suspected cancer. The NCD excludes the workup of suspected malignancy, so the chart must document the established cancer and the reason for the test.

Covered ICD-10 diagnosis codes to pair with CPT 86301

Every Medicare claim for CPT 86301 also needs an ICD-10-CM code for an established pancreatic or biliary ductal carcinoma, or its history. The table also separates the NCD’s core codes from codes only some commercial payers accept. Verify the current NCD 190.30 covered-code list before billing, because CMS revises the lab NCD code lists.

In contrast, codes from the K80-K87 range (gallstones, cholecystitis, pancreatitis) and R-codes for elevated lab values lead to denial when billed alone. Confirm each code in the CDC/NCHS ICD-10-CM tool, then check it against the NCD 190.30 code list. In addition, for pancreatic tail and overlapping sites, the C25.7 reference covers the “other parts of pancreas” code.

Medicare and payer coverage policies for CPT 86301

Medicare Part B covers CPT 86301 under NCD 190.30, Tumor Antigen by Immunoassay – CA 19-9, and pays it under the Clinical Laboratory Fee Schedule (CLFS). A national coverage determination applies in every Medicare Administrative Contractor (MAC) jurisdiction, so no local policy changes the rule.

First, the patient must have an established pancreatic or biliary ductal carcinoma. The test can then be repeated as needed to check for recurrence or response to each treatment cycle.

The coverage call comes down to two questions, and both are answered before the specimen is drawn:

Key Medicare coverage rules for CPT 86301:

• Covered: Following an established pancreatic or biliary ductal carcinoma, including treatment response and recurrence checks
• Not covered: Screening, or evaluating signs and symptoms that suggest a malignancy
• Not covered: Benign conditions (pancreatitis, cholestasis, IBS) as the sole ICD-10 diagnosis, even when CA 19-9 is elevated
• Outside the NCD: Monitoring hepatocellular, colorectal or gastric cancer. Treat these as payer-specific and issue an ABN for Medicare patients.
• ABN requirement: Issue an Advance Beneficiary Notice of Noncoverage (ABN) before the test when Medicare may not cover it for a specific patient. For instance, a chart that only lists benign pancreatitis is the classic example. Otherwise, the lab cannot bill the patient if Medicare denies the claim.
• Commercial payers: Coverage criteria and prior authorization requirements also vary. Check individual payer policies before assuming Medicare rules apply universally.

How to bill CPT 86301: modifiers, units, and place of service

Billing CPT 86301 correctly requires attention to who is submitting the claim, where the test is performed, and whether any modifiers apply. For example, a common error is the ordering provider’s office billing a test that an outside laboratory performed.

In contrast, practices that run CA 19-9 in-office under their own CLIA certificate bill 86301 themselves. Pabau, the practice management platform we build, generates CMS-1500 claims from invoices and sends them to thousands of US insurance payers through the Claim.MD clearinghouse. In addition, a real-time eligibility check (270/271) confirms the patient’s coverage before the test is performed.

CPT 86301 reimbursement rates: Medicare CLFS payment data

Medicare pays for CPT 86301 under the Clinical Laboratory Fee Schedule (CLFS). Its rates also come from private payer data reported under the Protecting Access to Medicare Act (PAMA). The 2026 rate for 86301 is $20.81, unchanged from 2025. Check the current figure in the CMS Clinical Laboratory Fee Schedule files before billing.

In contrast, commercial payer rates often use a multiplier of the CLFS rate. Overall, reimbursement can range from 80% to 150% or more of the Medicare allowable depending on the payer contract. Therefore, verify contracted rates directly with each payer; do not assume CLFS figures apply to commercial claims.

CPT 86301 vs related tumor marker codes: choosing the right code

The tumor marker codes sit next to each other, but each one maps to a single antigen. Thus, billing the wrong one reports a test the lab didn’t run, which is both a coding error and a compliance issue.

The most consequential confusion is between 86301 (CA 19-9) and 82378 (CEA). Both are also commonly ordered together for colorectal and pancreatic cancer patients. However, billing both on the same date of service is permitted when each has a separately documented clinical indication in the ordering note.

Billing one code when the lab ran the other is a coding error, whatever the dollar impact. Therefore, reference the AAPC CPT code lookup to confirm the correct descriptor before submitting.

Common denial reasons for CPT 86301 and how to avoid them

Denials for CPT 86301 follow predictable patterns, and most start with the ordering note rather than the claim form. That is why denial management for this code begins before the claim is created.

To begin with, review your medical billing denial codes to see whether CA 19-9 denials cluster around one claim adjustment reason code (CARC). For example, CARC 50 (not medically necessary), CARC 167 (diagnosis not covered) and CARC 96 (non-covered charge) can all apply to 86301.

Documentation requirements for successful CPT 86301 claims

The ordering provider’s note is the most auditable part of a CA 19-9 claim. In fact, an appeal turns on whether that note names the established pancreatic or biliary ductal carcinoma. It must also give the reason for the test in the terms NCD 190.30 uses.

Required documentation elements for a clean 86301 claim:

• Active or historical malignancy: The patient’s chart must contain an active cancer diagnosis or a documented history of a covered malignancy. The diagnosis must also be linked to the order in the same note or the most recent relevant visit note.
• Clinical rationale: The ordering note must state whether the test monitors treatment response or checks for recurrence. “Monitoring pancreatic cancer response to FOLFIRINOX” satisfies this requirement. “Repeat labs” does not.
• Date of service and ordering provider signature: Both are required on the lab requisition. Also, the ordering provider’s NPI must match the signature.
• CLIA number of the performing lab: Must appear on the claim itself, rather than just in the lab’s internal records.
• ICD-10 code alignment: The diagnosis codes on the claim must also match the active diagnoses documented in the patient’s record on the date of service. For example, submitting a C25.9 code when only K85.9 (pancreatitis) appears in the chart is a false claim risk.

In Pabau, the clinical note, the invoice and the claim built from that invoice all sit on the same patient record. When a payer questions an 86301 claim, your billing team finds the ordering rationale right beside it. As a result, nobody has to request notes from a separate EHR. That is also the groundwork for clean claim submission on in-office lab draws.

How Pabau supports CA 19-9 claim submission and follow-up

Practices that draw CA 19-9 in-house often juggle an EHR, a billing spreadsheet and a clearinghouse portal for one $20.81 test. Moreover, each handoff is a chance to drop a diagnosis code or lose track of a denial. Instead, Pabau’s claims management software keeps claim creation, submission and follow-up in one place.

Key workflow capabilities relevant to CPT 86301:

• Claims built from invoices: Pabau generates CMS-1500 claims from the visit invoice, so the codes already on the patient record carry over without retyping.
• Electronic submission via Claim.MD: Claims also go to thousands of US insurance payers through the Claim.MD clearinghouse, without leaving Pabau.
• Real-time eligibility checks: A 270/271 check confirms the patient’s coverage and benefits before the specimen is drawn.
• Claim status and ERA posting: Statuses also update from the payer. Electronic remittance advice (835 files) posts against the claim it settles, so an 86301 denial appears beside the original claim.

Knowing how medical billing works end to end shows you where CA 19-9 claims fail: documentation, coding or submission. With claims, eligibility and remittances in one system, you can also fix the weak step without adding billing staff.

Conclusion

Billing 86301 well comes down to one check before the draw. Does the patient have an established pancreatic or biliary ductal carcinoma, and is the test following it? If yes, then code the cancer or its history and write the purpose into the order.

Otherwise, issue an ABN or check the commercial payer’s policy before the specimen goes out. The effort is front-loaded on purpose. In short, a minute spent on the ordering note saves an appeal that a $20.81 test rarely justifies.

To see how Pabau takes a CA 19-9 claim from invoice to posted remittance in one system, book a demo.

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