CPT® Code 87804

Last Updated: February 2026 | Verified for 2026 AMA, CPT & CMS Guidance and Current CDC Testing Recommendations

Quick Reference: CPT 87804 (Rapid Influenza Antigen Test)

• What 87804 means: A rapid influenza A/B antigen test performed using an immunoassay with direct optical (visual) observation—commonly a point-of-care kit read visually rather than instrumented quantitation. CPT 87804 describes the test service, not an office visit or treatment.
• Where it is used: Most often performed in clinics, urgent care, physician offices, and other point-of-care settings to rapidly support influenza management decisions when patients present with influenza-like illness.
• When testing matters most: Medicare guidance and CDC recommendations emphasize that influenza testing should be used when results will influence management, and that molecular testing is recommended for hospitalized patients with suspected influenza. Rapid antigen tests are faster but generally less sensitive than molecular methods, and confirmatory testing may be needed depending on influenza activity and clinical context.
• CLIA-waived billing marker: When the performed test is CLIA-waived, many Medicare and Medicaid workflows require appending modifier QW to identify a waived test (payer processing is driven by CLIA requirements and code/modifier rules).
• Influenza A and B results and “two units”: Some payer policies allow billing two units of 87804 when a single encounter produces distinct influenza A and influenza B results from testing (for example, dual targets reported). Plan rules may specify how the second unit must be submitted (e.g., modifier use).
• Avoid the most common denial patterns: (1) missing CLIA-waived modifier reporting when required, (2) billing two influenza tests in the same encounter when payer policy covers only one diagnostic influenza test per visit, (3) using 87804 when the actual method does not meet the “direct optical observation” definition, and (4) weak documentation of medical necessity and symptom onset timing. CPT 87804 is a rapid influenza diagnostic test (RIDT) code used for antigen-based influenza testing performed via an immunoassay read by direct visual observation.

In practice, it is commonly used during influenza season when a symptomatic patient presents with fever and respiratory symptoms and a clinician needs a rapid result to support decisions such as antiviral treatment, isolation advice, and differential diagnosis (especially when other respiratory viruses are circulating).

CMS billing guidance and CDC clinical recommendations are the anchor references for defensible use: they explain where rapid antigen tests fit, when confirmatory molecular testing is appropriate, and how test selection should track clinical setting (outpatient vs hospitalized) and local influenza activity.

1. Clinical Definition and Scope of CPT 87804

CPT 87804 describes a rapid influenza diagnostic test performed using an immunoassay with direct optical observation. Operationally, this is the classic “rapid flu antigen” test where a nasal or nasopharyngeal specimen is processed in a test device and the result is read visually by clinical staff (e.g., a line-based or color-change readout). CMS and coding references identify 87804 within the family of influenza diagnostic test codes and distinguish it from other influenza testing methodologies such as molecular amplification methods.

From a compliance standpoint, two boundaries matter:

• Method boundary: 87804 is appropriate when the test is an immunoassay read by direct optical observation. If the performed test is an instrumented molecular assay (e.g., nucleic acid amplification), it should be coded with a molecular influenza code rather than 87804. CMS guidance explicitly highlights molecular testing as a distinct diagnostic method and recommends it for hospitalized patients.
• Clinical-use boundary: Rapid antigen tests provide speed but have recognized limitations in sensitivity compared to molecular methods, which affects when confirmatory testing is appropriate and how negative results are interpreted in high-prevalence settings. CDC clinician guidance describes these interpretation and confirmation principles. Practical compliance point: The test method documented in the chart (and often implicitly in the product name/test platform) must align with the code billed. If the site used a molecular platform (rapid NAAT/RT-PCR), auditors and payers expect a molecular influenza test code—not 87804—even if the result was returned quickly.

2. When Rapid Antigen Testing Is Clinically Appropriate

CDC clinician guidance positions rapid influenza diagnostic tests (RIDTs) as tools that may assist clinical management, especially when a timely result can influence treatment and infection-control decisions. The strongest clinical fit for RIDTs is typically symptomatic outpatients early in illness when a rapid result supports time-sensitive decisions (for example, antiviral initiation in higher-risk patients). CDC also emphasizes that specimen collection timing matters—respiratory specimens collected early (often within the first several days of symptoms) are more likely to yield a detectable viral burden.

CMS Medicare billing and coding guidance similarly frames influenza testing in a stewardship and medical-necessity context: point-of-care clinicians should consider testing prior to prescribing antibiotics when influenza is in the differential, but testing is not clinically required for every outpatient once influenza is documented in the community. Critically, CMS guidance states that molecular influenza testing is recommended for hospitalized patients with suspected influenza, reflecting the higher-stakes setting and the need for higher diagnostic performance.

A defensible, payer-realistic approach is to document:

• Why test now: symptoms consistent with influenza and why the result influences management (antivirals, work restrictions, isolation counseling, differential diagnosis).
• Timing: symptom onset date/time (or at least day of illness) to support appropriate RIDT interpretation and clinical use.
• Setting selection: outpatient RIDT vs inpatient molecular testing rationale, consistent with CMS and CDC recommendations.

3. CMS Billing Rules: CLIA, QW, and Practical Claim Submission

Influenza testing claims are evaluated through a combination of coding correctness, CLIA requirements, and medical necessity. CMS billing and coding guidance for influenza diagnostic tests provides the Medicare framework for covered diagnostic approaches, describes testing methods, and includes coding information relevant to claim submission, including modifier conventions that may apply to point-of-care testing workflows.

3.1 CLIA-waived testing and modifier QW

In routine practice, many rapid antigen influenza tests are CLIA-waived when performed with waived test kits according to their labeling. For Medicare and many Medicaid programs, the waived nature of a test is often communicated on the claim by appending modifier QW when required by payer processing rules for CLIA-waived tests. CMS influenza testing guidance includes coding elements that support compliant submission patterns for influenza diagnostic testing claims.

Compliance steps for waived testing workflows typically include:

• Maintain an active CLIA certificate consistent with the testing complexity performed.
• Ensure the specific influenza rapid test used is waived and performed according to manufacturer instructions.
• Apply claim formatting (including modifiers) consistent with payer requirements for waived tests.

3.2 Code family context and CMS code listings

CMS has published code fact sheets and guidance documents that list influenza-related diagnostic test codes and descriptors in policy contexts. These resources are useful for confirming how CMS labels the code families and how influenza, RSV, and related testing codes are presented operationally.

4. Documentation Standards That Support Medical Necessity

Medical necessity is the core driver of coverage for diagnostic testing. Across Medicare and commercial plans, documentation should show that (1) the patient has symptoms consistent with influenza or a clinically appropriate reason for testing, and (2) the test result will influence management. CMS influenza testing guidance explicitly describes when outpatient testing may or may not be needed and stresses that molecular methods are recommended in hospitalized patients.

4.1 Minimum documentation elements (audit-practical)

• Symptoms and clinical context: fever, cough, sore throat, myalgias, malaise, shortness of breath (as applicable), plus relevant exposure or outbreak context.
• Symptom onset timing: document when symptoms began; CDC guidance emphasizes early specimen collection and provides interpretation guidance tied to community influenza activity and pretest probability.
• Specimen type and collection: nasal/nasopharyngeal specimen (or other respiratory specimen used), and that collection followed the test manufacturer’s instructions (CDC highlights following manufacturer instructions).
• Test performed and result: name/description of the rapid influenza antigen test, and the result(s) reported (Influenza A, Influenza B, or both/negative as applicable).
• Clinical action: how the result influenced management (antiviral initiation, avoidance of antibiotics when influenza is likely, additional testing, escalation to molecular testing, or infection-control counseling). Documentation risk pattern: A chart that only says “rapid flu test done” without influenza-like illness documentation, symptom onset, or a management link is vulnerable in medical-necessity review—especially when payers apply policies limiting routine testing or limiting multiple influenza tests in one encounter.

5. Units, Modifiers, and Common Edits (A vs B Reporting)

Billing patterns for 87804 vary because influenza testing workflows vary. Some rapid tests produce a single combined “Influenza A/B” output; others produce separate A and B results; some organizations bill a single unit regardless of dual targets; and some payers specify when two units may be billed. The defensible approach is to follow (1) the test’s reporting structure, (2) CMS guidance where applicable, and (3) the patient’s payer policy for units and modifier rules.

5.1 Reporting two results (Influenza A and Influenza B)

When an encounter legitimately produces distinct influenza A and influenza B results and payer policy allows separate reporting, some plans explicitly allow billing two units of CPT 87804. For example, Blue Cross Oklahoma’s diagnostic testing policy states conditions under which two units can be billed when both A and B are detected/reported.

Practical claim hygiene when billing two units:

• Ensure the record clearly shows that both targets were tested and results were produced (A result and B result).
• Follow payer-specific instructions on whether the second line requires a distinctness modifier or other claim formatting.
• Do not assume “two results” automatically means “two billable units” for every payer; verify payer rules, especially for plans that limit one influenza diagnostic test per encounter.

5.2 Repeat testing and confirmatory testing

CDC guidance describes circumstances where confirmatory molecular testing may be appropriate depending on community influenza activity and RIDT result patterns (e.g., positive results when community activity is low, or negative results when community activity is high). This is clinical logic, but it can also support medical necessity for a second test when performed appropriately and documented as confirmatory.

Separately, payer medical policies may limit coverage for multiple influenza diagnostic tests in a single encounter (for example, covering either a rapid antigen test or a rapid molecular test but not both for the same visit unless specific criteria are met). UnitedHealthcare’s policy framework and other plan policies are commonly written this way: they describe covered influenza diagnostic testing methods and conditions, which can affect whether multiple tests are payable.

6. Payer Policies: Medicare Direction and Commercial Plan Patterns

6.1 Medicare (CMS guidance anchor)

CMS Medicare billing and coding guidance for influenza diagnostic tests is a primary authoritative reference because it frames influenza testing within “reasonable and necessary” principles and describes the test categories available (rapid antigen, molecular, culture). It emphasizes stewardship considerations and explicitly states that molecular methods are recommended for hospitalized patients with suspected influenza. This guidance supports the operational distinction that outpatient rapid antigen testing may be reasonable when it influences management, but it is not mandatory for all outpatients during periods of documented community influenza activity.

6.2 UnitedHealthcare

UnitedHealthcare’s Diagnostic Testing of Influenza policy is important because it represents a large national payer’s coverage logic and coding criteria for influenza testing. It lists CPT 87804 among covered influenza diagnostic tests when billed consistent with policy requirements and clinical presentation. In practice, UHC policy language can influence denials related to diagnosis-code support, test duplication within an encounter, and restrictions on non-recommended test categories.

6.3 Aetna

Aetna’s clinical policy bulletin on influenza rapid diagnostic tests similarly describes when influenza testing is medically necessary and includes CPT 87804 in its policy listing. For organizations that see mixed payer populations, Aetna policy is commonly used in internal compliance crosswalks to anticipate denial reasons (especially documentation of influenza-like illness and clinical rationale for testing).

6.4 Blue Cross/Blue Shield example (units and visit limits)

Blue Cross plan policies can be highly specific about unit billing, encounter limits (e.g., one influenza diagnostic test per visit), and when multiple results justify separate billing. Blue Cross Oklahoma’s diagnostic testing policy is an example of a plan document that explicitly addresses influenza testing and includes guidance relevant to billing two units when both influenza A and B are detected/reported.

Payer reality: For influenza testing, “clinically reasonable” does not always mean “paid twice.” When an RIDT is followed by a molecular assay, the record should clearly document why confirmatory testing was needed (CDC describes confirmation logic tied to influenza activity and result patterns), and the claim should follow payer policy rules on duplicates and covered methods.

7. Comparison Table: 87804 vs Molecular Influenza Tests and Related Codes

Correct code selection depends on methodology and clinical setting. CMS guidance distinguishes rapid antigen testing from targeted molecular methods and explains why molecular methods are recommended for hospitalized patients with suspected influenza. CDC guidance provides interpretation and confirmation recommendations for rapid influenza diagnostic tests.

8. Real-World Clinical Scenarios and Clean Coding Examples

Scenario 1: Symptomatic outpatient during influenza season (rapid decision support)

Setting: Urgent care / office.

Presentation: Fever, cough, myalgias, symptom onset 24–48 hours ago.

Service: Point-of-care RIDT performed and read visually; influenza A detected.

Coding logic: Bill 87804 (and QW if required for the waived test), linking the line to influenza-like illness documentation and symptom onset timing. Document how the result influenced management (e.g., antiviral therapy, counseling). CDC guidance supports early specimen collection and context-dependent interpretation.

Scenario 2: Dual target reporting (Influenza A and B results reported in one encounter)

Setting: Outpatient clinic using a rapid antigen test device that reports both A and B results.

Service: Both influenza A and influenza B results are produced/reported (per test output).

Coding logic: If the payer policy allows, bill 87804 with two units following plan-specific submission rules. Blue Cross Oklahoma policy is an example that addresses two-unit billing logic in defined circumstances.

Scenario 3: Hospitalized patient with suspected influenza (method selection)

Setting: Hospital inpatient / ED admission.

Presentation: Severe influenza-like illness; clinician needs higher diagnostic certainty.

Service: Molecular influenza testing ordered/performed rather than RIDT due to clinical setting and performance needs.

Coding logic: Use the appropriate molecular influenza testing code rather than 87804 when the method is NAAT/RT-PCR. CMS guidance explicitly states molecular methods are recommended for hospitalized patients with suspected influenza.

Scenario 4: Negative RIDT when influenza activity is high (confirmatory testing rationale)

Setting: Outpatient clinic during high community influenza activity.

Presentation: High pretest probability; RIDT negative; clinician considers confirmation.

Service: Specimen sent for molecular confirmation based on CDC guidance principles (negative RIDT in high-activity setting may warrant confirmation).

Coding logic: Document the clinical rationale for confirmatory testing and follow payer policy regarding multiple tests in one encounter. CDC provides the interpretive logic that supports confirmation in defined situations.

9. Common Billing Pitfalls and How to Prevent Denials

• Pitfall 1: Missing CLIA-waived claim indicator when required. Why it denies: Payers may treat waived testing as nonpayable or incomplete without proper claim formatting for CLIA-waived tests.

Prevention: If the performed test is waived and payer rules require it, append QW and ensure your CLIA certificate status supports the performed testing.

• Pitfall 2: Billing 87804 when the actual platform is molecular. Why it denies: Code-to-method mismatch is detectable through test platform documentation, lab records, or audit requests. CMS guidance separates rapid antigen testing from targeted molecular methods and recommends molecular methods for hospitalized patients.

Prevention: Build an internal crosswalk (test platform → CPT/HCPCS) and require staff to document the test name/platform in structured fields.

• Pitfall 3: Weak medical-necessity narrative (no symptoms, no onset, no management impact). Why it denies: Influenza diagnostic testing is evaluated under reasonable-and-necessary principles, and both CMS and CDC describe contexts where testing is not needed for all outpatients once influenza is circulating in the community.

Prevention: Document influenza-like illness symptoms, onset timing, and why the result influenced management; align with CDC specimen collection and interpretive recommendations.

• Pitfall 4: Two influenza tests in one encounter without a documented confirmatory rationale. Why it denies: Many payer policies cover one diagnostic influenza test per visit or limit multiple tests unless specific criteria are met; policies can be method-specific (RIDT vs molecular).

Prevention: When confirmatory testing is clinically indicated, document the CDC-supported rationale (activity level + result pattern) and follow payer policy requirements for duplicates.

• Pitfall 5: Billing two units without a payer-supported rule or without clear A/B result reporting. Why it denies: Plans vary on whether they treat dual target reporting as one payable test or two payable units; some provide explicit unit instructions.

Prevention: Confirm the plan policy; ensure documentation shows distinct reported results. A BCBSOK policy example specifically addresses two-unit reporting logic in defined circumstances.