CPT® Code 81528

Quick Reference

• Code definition: CPT 81528 reports the multi-target stool DNA (mt-sDNA) assay, commercially known as Cologuard, which analyzes a stool specimen for 10 DNA markers (KRAS mutations, NDRG4 and BMP3 promoter methylation) combined with a fecal immunochemical test for hemoglobin, reporting a binary positive or negative result for colorectal cancer screening.
• Key billing rule: Only the performing laboratory bills CPT 81528. Ordering and referring physicians do not submit this code; claims from ordering providers are denied. The ordering provider's NPI appears in the referring provider field only. [7]
• Payment system: 81528 is a Statutory Exclusion from the Medicare Physician Fee Schedule and is paid exclusively under the Clinical Laboratory Fee Schedule (CLFS). No facility or non-facility RVU split applies and no TC or 26 modifier is appropriate. [4]
• Modifier essentials: Append modifier GA when an ABN has been obtained before collection for a non-covered claim (frequency not met, age outside range). Use modifier GZ when no ABN was issued but denial is anticipated. Append modifier 33 for commercial payers to signal ACA preventive service status; do not append modifier 33 on Medicare claims. [1]
• Documentation must-have: The ordering record must explicitly confirm average-risk status: asymptomatic, no prior colorectal cancer, no prior adenomatous polyps, no inflammatory bowel disease, and no family history that elevates the patient to high-risk. [1]
• Top confusion point: CPT 82274 (fecal hemoglobin immunoassay, FIT) is an integral analytic component of the 81528 assay. Billing 82274 on the same date constitutes unbundling and will be denied or recouped on audit. [2]
• CLIA requirement: 81528 is not CLIA waived. The performing laboratory must hold high-complexity CLIA certification. Physician office labs and point-of-care settings cannot perform or bill this test. [4]
• MUE: 1 unit per date of service. One stool submission equals one complete test episode; multiple units generate automatic denials. [3]

When to Use This Code

CPT 81528 applies specifically when a stool-based mt-sDNA test is performed for colorectal cancer screening in an average-risk patient. Under CMS NCD 210.3 [1], covered patients are asymptomatic individuals age 45 through 85 who meet all four average-risk criteria: no prior colorectal cancer history, no prior adenomatous polyps, no inflammatory bowel disease, and no family history qualifying them as high risk. The age floor was lowered from 50 to 45 effective January 1, 2023 per the Consolidated Appropriations Act, 2023 [9], aligning Medicare coverage with the USPSTF Grade B recommendation for adults age 45 to 49.

The test applies only as preventive screening, not as a diagnostic tool. Patients presenting with active gastrointestinal symptoms including hematochezia, unexplained iron-deficiency anemia, or other CRC-related symptoms do not qualify; their workup requires diagnostic codes and appropriate diagnostic tests. Post-polypectomy surveillance and high-risk monitoring require colonoscopy-based pathways, not 81528.

81528 is a laboratory-only code. The performing laboratory (such as Exact Sciences, which processes Cologuard specimens at its CLIA-certified facility) submits the claim. Stool collection is performed by the patient at home and mailed directly to the laboratory; there is no separately billable specimen collection charge on the lab's claim. The ordering provider (primary care physician, internist, or qualified NPP) writes the order and does not submit 81528 charges.

Frequency: Medicare covers 81528 once every three years. The performing laboratory carries the obligation to verify coverage eligibility before processing a specimen, because frequency denials where no ABN was issued result in the laboratory absorbing the full cost.

Code Differentiation Table

The sharpest clinical distinction is between 81528 and G0327: both are noninvasive CRC screening modalities for average-risk patients under NCD 210.3, but they correspond to entirely different test methodologies and must not be billed for the same screening interval. Select the code that matches the test actually performed.

flowchart TD
    A[CRC Screening Order] --> B{Patient age 45 to 85?}
    B -->|No| C[Not covered under NCD 210.3\nIssue ABN if ordered]
    B -->|Yes| D{Average risk: asymptomatic\nno prior CRC, adenoma, or IBD?}
    D -->|No: High risk| E[Order colonoscopy: G0105\n81528 not covered]
    D -->|Yes| F{Stool-based test ordered?}
    F -->|No: Blood-based test| G[Bill G0327 with Z12.11]
    F -->|Yes| H{3-year interval met\nsince prior sDNA test?}
    H -->|No: Too soon| I[Issue ABN before collection\nBill GA or GZ]
    H -->|Yes| J[Bill 81528 with Z12.11]

Billing and Modifier Rules

Billing party and claim structure. The performing laboratory submits CPT 81528 on a CMS-1450 (UB-04) or CMS-1500 claim, depending on entity type. The ordering provider's NPI populates the referring/ordering provider fields. No professional or technical component split applies (PC/TC Indicator 9); modifier 26 and TC are never appropriate. [4]

Modifier GA. Append when the laboratory issues an ABN before specimen collection, notifying the patient that Medicare may deny the claim due to unmet coverage criteria (frequency restriction, age outside the covered range, or inability to confirm average-risk status). The patient is financially liable for the CLFS-allowed amount. The ABN must be signed prior to specimen collection; retroactive ABNs are invalid. [1]

Modifier GZ. Append when no ABN was obtained but denial is expected. This signals that the laboratory absorbs the cost; the patient cannot be billed. Routine GZ billing on a predictably non-covered service raises audit scrutiny.

Modifier 33. Do not append to Medicare claims; 81528 is inherently recognized as a preventive service under the Medicare colorectal cancer screening benefit and no modifier is required to trigger zero cost-sharing. Append modifier 33 on claims to commercial payers to signal ACA-mandated preventive service status where applicable, but confirm individual plan policy. [1]

No modifier 59 or X-modifiers. There is no valid NCCI bypass scenario for 81528. It is a standalone assay. Attempts to unbundle component services using modifier 59 are incorrect and will not withstand audit. [2]

No modifier 51. Multiple procedure reduction does not apply (Indicator 9). No bilateral surgery modifiers or assistant surgeon modifiers are relevant. [4]

MUE and units. The Medically Unlikely Edit is 1 unit per date of service [3]. A single stool submission yields one complete test episode. Multiple units will trigger automatic denial.

Bundling: 82274 is non-separately billable. The fecal hemoglobin immunoassay is an integral analytic component of the sDNA-FIT assay. NCCI Policy Manual Chapter 9 [2] governs molecular pathology component bundling; 82274 is bundled into 81528 and modifier 59 does not override this because the services are clinically inseparable.

Bundling: 82270 on same date. The guaiac fecal occult blood test and the mt-sDNA assay are mutually exclusive CRC screening methodologies. Billing 82270 alongside 81528 on the same date of service is inappropriate.

G0327 mutual exclusion. Billing both 81528 and G0327 for the same screening episode is not appropriate. Only one noninvasive screening modality should be used per coverage interval.

Documentation Essentials

Average-risk status is the single most audited element. The laboratory order and supporting clinical documentation must explicitly confirm all four average-risk criteria: asymptomatic status, no prior colorectal cancer, no prior adenomatous polyps, and no qualifying family history. A check-box order form without supporting clinical context will not satisfy audit requirements; the ordering provider's notes should reflect this assessment. [1]

Required documentation elements for each claim:

• Patient date of birth confirming age 45 to 85 at time of specimen collection
• Signed physician or qualified NPP order with ordering provider NPI
• Explicit attestation of average-risk and asymptomatic status in the order or clinical notes
• Date of prior sDNA test (or documentation that this is the first test) supporting the three-year frequency interval
• Signed and dated ABN if applicable, with patient signature obtained before specimen collection

Audit red flags specific to 81528. MACs and Recovery Audit Contractors target 81528 claims when the primary diagnosis reflects symptoms rather than screening (K92.1, rectal bleeding codes), when the frequency interval is under three years based on prior claim history, or when the ordering provider NPI matches the performing laboratory's NPI. Claims for patients with documented history of adenomatous polyps (Z86.010) are particularly vulnerable because that history disqualifies the patient from the average-risk benefit; auditors cross-reference this against the claim. [1]

Diagnosis code selection. The primary claim diagnosis must be Z12.11 (encounter for screening for malignant neoplasm of colon) for standard preventive colorectal cancer screening. Z12.12 (rectum) is an alternative when clinically appropriate. Do not use family history codes (Z80.0) as the primary diagnosis for average-risk screening; a qualifying family history may actually elevate the patient to high-risk status and disqualify the claim.

Medicare, Commercial, and Medicaid Payer Rules

Medicare

CPT 81528 is covered under NCD 210.3 (Colorectal Cancer Screening) [1], which governs eligibility, frequency, and age criteria:

• Covered ages: 45 through 85, expanded from 50 to 45 effective January 1, 2023, per CAA 2023 [9]
• Frequency: Once every three years
• Beneficiary cost-sharing: $0 deductible and $0 coinsurance when correctly coded as preventive screening with Z12.11
• Payment: CLFS rate, not MPFS. Verify the CY2026 CLFS rate at the CMS Clinical Laboratory Fee Schedule page [4]; historical rates have ranged approximately $508 to $512 with ongoing PAMA-mandated adjustments.
• CLIA: High-complexity certification required; not CLIA waived [4]

Follow-up colonoscopy after a positive result. Under the Consolidated Appropriations Act 2021, effective January 1, 2022 [8], a follow-up colonoscopy performed after a positive 81528 result retains preventive benefit status for Medicare cost-sharing purposes. The coinsurance reduction is phased, beginning at 20% in 2022 and increasing annually, reaching 0% by 2030. The 81528 claim and the colonoscopy claim are entirely separate; the colonoscopy is billed by the gastroenterologist on the date of the procedure. This provision has significant impact on patient counseling and downstream billing; confirm current MAC guidance on the appropriate colonoscopy code when both diagnostic and preventive billing considerations apply.

Commercial Payers

Many commercial plans follow USPSTF recommendations and cover mt-sDNA for average-risk adults age 45 and older, but plan-specific policies govern frequency, prior authorization requirements, and network restrictions for the performing laboratory. Append modifier 33 as appropriate to signal ACA preventive service status and trigger zero cost-sharing under plans following ACA mandates. Not all commercial plans treat 81528 as preventive for all covered ages; verify each plan's policy before the laboratory processes a commercial patient's specimen. [1]

Medicaid

Coverage varies by state and managed Medicaid plan. Some state programs cover 81528; others do not or impose prior authorization requirements. Verify with the applicable state Medicaid agency or managed care plan. No uniform federal Medicaid coverage requirement governs 81528.

Common Denials and Prevention

Ordering provider bills 81528

The ordering physician or NPP submits 81528 on a professional claim, sometimes under the mistaken belief they are billing for order management or clinical interpretation. Only the performing laboratory submits this charge. Prevention: ensure billing and coding staff at ordering practices understand that 81528 never appears on a physician's CMS-1500. If the laboratory submits G0452 for physician interpretation, confirm whether that service is separately covered and billed by the laboratory's medical director, not the ordering provider.

Frequency exceeded

Medicare cross-references prior 81528 claim data. A claim submitted fewer than three years after a prior sDNA test will be denied. Prevention: the performing laboratory must query prior claim history before processing. When frequency cannot be confirmed and the test proceeds, issue an ABN before specimen collection and append modifier GA. If no ABN was issued, append modifier GZ and absorb the cost; retroactive patient billing is not permitted. [1]

Non-screening diagnosis code as primary

Using a symptom-based or diagnostic code (K92.1, rectal bleeding, or any active CRC code) as the primary diagnosis converts the claim from a preventive to a diagnostic service. This eliminates zero cost-sharing, triggers beneficiary cost-sharing obligations, and may prompt medical necessity review. Prevention: confirm the primary diagnosis is Z12.11 for all standard average-risk preventive claims. When a patient has symptoms that prompted the order, advise the ordering provider that 81528 is clinically and administratively inappropriate for symptomatic workup. [1]

High-risk patient coded as average risk

Claims for patients with documented history of colorectal adenomas (Z86.010), prior CRC, IBD, or qualifying family history are not covered under the NCD 210.3 average-risk benefit. MACs identify these patients through diagnosis cross-referencing and prior claims analysis. Prevention: the ordering provider must screen patient history before ordering; the laboratory should implement order review checkpoints. When a high-risk indicator is identified after an order is received, contact the ordering provider before processing. These patients should be referred for colonoscopy surveillance, not sDNA screening. [1]

Unbundling 82274 alongside 81528

Laboratories that separately charge for the FIT hemoglobin component of the Cologuard assay will have the 82274 claim denied or face recoupment on RAC audit. NCCI Policy Manual Chapter 9 [2] governs molecular pathology component bundling. Prevention: configure billing systems so 82274 cannot be submitted on the same claim as 81528. Modifier 59 does not override this bundling relationship.

Coding Scenarios

Scenario 1: A 67-year-old asymptomatic Medicare beneficiary with no prior CRC history, no adenomas, and no IBD presents for her annual wellness visit. Her internist orders Cologuard. She returns a stool sample collected at home, which she mails to the performing laboratory.

Correct coding (by laboratory): 81528 with Z12.11

Why: The patient meets all average-risk criteria and falls within the covered age range. The internist bills the AWV (G0439 or G0438) only; the internist does not submit 81528. Beneficiary cost-sharing is $0 under the Medicare preventive benefit. [1]

Scenario 2: A 72-year-old Medicare patient completed a Cologuard test 20 months ago with a negative result. His new primary care provider, unaware of the prior test, orders Cologuard again.

Correct coding if ABN was issued before collection: 81528 with modifier GA and Z12.11. The patient is responsible for the full CLFS-allowed amount.

Correct coding if no ABN was issued: 81528 with modifier GZ. The laboratory absorbs the cost; the patient cannot be billed.

Why: The three-year frequency has not elapsed. Medicare will deny the claim. The distinction between GA and GZ determines financial responsibility. [1]

Scenario 3: A 58-year-old average-risk Medicare beneficiary receives a positive Cologuard result. Her gastroenterologist performs a follow-up diagnostic colonoscopy; no lesions are identified.

Correct coding (by gastroenterologist/facility): 45378 with Z12.11. The 81528 claim was already adjudicated separately by the laboratory.

Why: Under the Consolidated Appropriations Act 2021 [8], a follow-up colonoscopy after a positive sDNA result retains preventive benefit character for cost-sharing purposes. The colonoscopy is billed on its own date of service. Beneficiary coinsurance applies at a reduced rate per the CAA 2021 phase-in schedule; confirm current MAC guidance on the appropriate colonoscopy code and cost-sharing percentage for the claim year.

Scenario 4: A 55-year-old patient had a 1.5 cm tubular adenoma removed during colonoscopy four years ago. Her physician orders Cologuard for "routine colorectal cancer screening."

Correct action: Do not bill 81528 as a covered service. The laboratory should contact the ordering provider before processing the specimen.

Why: Personal history of adenomatous polyps (Z86.010) is a high-risk indicator; NCD 210.3 [1] restricts 81528 to average-risk patients. This patient requires colonoscopy surveillance (45378 through 45392) billed with appropriate diagnosis codes for adenoma history. If the ordering provider insists on proceeding, issue an ABN before specimen collection and append modifier GA.

Related Codes

• G0327: Colorectal cancer screening, blood-based biomarker (alternative noninvasive CRC screening under NCD 210.3; mutually exclusive with 81528 per screening interval)
• G0121: Colorectal cancer screening colonoscopy, average risk (covered every 10 years; alternative to 81528 for average-risk patients who prefer colonoscopy)
• G0105: Colorectal cancer screening colonoscopy, high risk (used when patient history disqualifies them from 81528 average-risk coverage)
• 82274: Fecal hemoglobin by immunoassay, FIT (integral component of 81528; never separately billable on the same date)
• 82270: Fecal occult blood, guaiac, CRC screening (alternative stool-based screening methodology; mutually exclusive with 81528 on same date)
• 45378: Colonoscopy, flexible, diagnostic (follow-up after positive 81528 result; billed separately by the gastroenterologist on procedure date)
• Z12.11: Encounter for screening for malignant neoplasm of colon (required primary diagnosis for covered 81528 preventive claims)
• Z12.12: Encounter for screening for malignant neoplasm of rectum (alternative screening diagnosis when clinically appropriate)
• Z86.010: Personal history of colon polyps (history that disqualifies a patient from 81528 average-risk coverage; audit trigger)

Sources

1. CMS Medicare Coverage Database, NCD 210.3: Colorectal Cancer Screening — Primary governing policy for 81528 Medicare coverage, eligibility criteria, frequency, and average-risk requirements.
2. CMS NCCI Policy Manual, Chapter 9: Pathology and Laboratory — Bundling rules for molecular pathology codes, including the 82274/81528 relationship. Updated annually.
3. CMS NCCI MUE Tables — MUE value of 1 per date of service for CPT 81528. Updated quarterly.
4. CMS Clinical Laboratory Fee Schedule — CLFS payment rates for 81528; CLIA and MPFS status indicators. Updated annually per PAMA market survey methodology.
5. CMS Preventive Services: Colorectal Cancer Screening — Medicare preventive colorectal cancer screening coverage overview including 81528.
6. CMS Medicare Learning Network: Colorectal Cancer Screening Fact Sheet — Practitioner guidance on billing and coverage for colorectal cancer screening codes.
7. AMA CPT Code Set, CPT 81528 — Official CPT descriptor; added effective January 1, 2016. Confirm Cologuard Plus code assignment in the AMA CPT 2026 codebook.
8. Federal Register, Consolidated Appropriations Act 2021 (CAA 2021), enacted December 2020, effective January 1, 2022 — Statutory basis for reduced beneficiary cost-sharing on follow-up colonoscopies after a positive sDNA screening result, with coinsurance phased to 0% by 2030.
9. Federal Register, Consolidated Appropriations Act 2023, enacted December 2022, effective January 1, 2023 — Age threshold reduction from 50 to 45 for average-risk colorectal cancer screening benefit, aligning with USPSTF Grade B recommendation.