CPT code 87635 – SARS-CoV-2 nucleic acid amplified probe test

Key takeaways

CPT Code 87635 covers SARS-CoV-2 detection by amplified probe (NAAT or PCR) only, not antigen-based rapid tests.

Lab-based 87635 tests need a moderate- or high-complexity CLIA certificate, while FDA-authorized point-of-care NAATs run under a certificate of waiver bill as 87635QW.

Do not bill 87635 and HCPCS U0004 on the same claim for the same test, because they describe alternative throughput levels.

Since the PHE ended on May 11, 2023, many commercial plans apply cost-sharing, while Medicare still covers ordered lab tests with no deductible or coinsurance.

Practice management software like Pabau runs validation checks in the background before you send a claim, so missing claim details are caught before submission.

CPT Code 87635: official descriptor and what it covers

CPT Code 87635 covers SARS-CoV-2 detection by an amplified probe technique, the nucleic acid amplification test (NAAT) family. The full AMA descriptor reads:

Infectious agent detection by nucleic acid (DNA or RNA); severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (coronavirus disease [COVID-19]), amplified probe technique.

The code belongs to the 87471-87801 infectious agent detection family, specifically the nucleic acid subsection. The key operative word is amplified probe technique, which means the lab must perform a NAAT-based method: RT-PCR, TMA, or a comparable amplification chemistry. Any test relying solely on antigen-antibody binding does not qualify, regardless of how the result is reported.

Acceptable specimens include nasopharyngeal, anterior nasal and oropharyngeal swabs, plus saliva. Each qualifies only where the test’s FDA Emergency Use Authorization (EUA) or clearance names that specimen type. Billing 87635 for a specimen not listed in the test’s EUA is a documentation risk during post-PHE audits. Verify the performing laboratory’s EUA authorization before submitting.

Accepted ICD-10 diagnosis codes to pair with CPT 87635

The ICD-10-CM code you attach tells the payer whether the claim is a diagnostic test or a screening test. That distinction affects patient cost-sharing and coverage eligibility. Verify the patient’s insurance eligibility before submitting any 87635 claim.

Individual payer coverage policies vary. Z11.52 does not guarantee coverage for a diagnostic-intent test under all payers post-PHE. Document the clinical rationale in the ordering note: symptoms, exposure history, or pre-procedure screening requirement. Payers running medical necessity edits will look for that documentation on audit.

Medicare reimbursement and CPT 87635 fee schedule for 2026

CPT Code 87635 is reimbursed under the Clinical Laboratory Fee Schedule (CLFS), not the Physician Fee Schedule. CMS sets one national CLFS rate each year, with no adjustment by locality. Billing software that runs validation checks before a claim is sent, as Pabau does, catches missing claim details before the payer sees them.

Confirm the 2026 national limitation amount for 87635 in the CMS Clinical Laboratory Fee Schedule before billing, because rates update each January 1. As of 2025, the national limitation amount was in the $50-75 range.

The PHE-era figure that still circulates is misleading for this code. CMS paid a temporary $100.00 rate for high-throughput HCPCS codes U0003 and U0004, not for 87635. Standard-throughput 87635 was paid about $51.31 during the PHE, and it now follows the standard CLFS methodology.

CPT 87635 vs U0003 and U0004: which code to use

The most common coding error on COVID-19 NAAT claims is choosing between 87635 and the HCPCS Level II codes U0003 and U0004. Per CMS guidance, the distinction comes down to throughput capacity, not the underlying PCR chemistry.

Never bill 87635 and U0004 on the same claim for the same SARS-CoV-2 test encounter. They describe mutually exclusive levels of throughput for the same analyte, and CMS bundling edits will deny the lower-value code. CMS Ruling 2020-1-R2 defines high throughput as automated processing of more than 200 specimens a day. Check current CMS transmittals for the billing status of U0003 and U0004 before using them post-PHE.

Related codes: CPT 87636, 87637, 87631, 87811, and 87804

When a physician orders a respiratory panel rather than a single-analyte COVID-19 test, the code selection shifts. Getting this wrong is one of the most common downcoding errors in lab billing. Verify code selection against the AAPC CPT code lookup if the test report lists multiple target analytes.

When a lab runs a multiplexed panel covering SARS-CoV-2, influenza A/B, and RSV on a single reaction, bill 87637, not 87635 plus individual codes. Unbundling a multiplex panel into its component single-analyte codes is an NCCI edit violation. The test report’s list of analytes is the deciding document, and the four checks below put the code choice in order.

Billing rules: modifiers, place of service, and bundling restrictions

Correct place of service (POS) coding for 87635 depends on where the specimen is collected and who performs the test. Using the wrong POS is a top denial trigger for reference lab claims. Send each one as a clean claim, with the correct POS and the performing lab’s CLIA number in Box 23 of the CMS-1500. Submitting 87635 claims electronically on an 837 file reduces the POS transcription errors common on paper claims.

The collecting provider, not the reference lab, can bill specimen collection in addition to 87635. That means 99000 for a transported specimen, or 36415 for venipuncture where applicable. Payer policies on collection add-on codes vary, so check the payer’s rules before the claim leaves your system.

Why CPT 87635 claims get denied and how to fix them

Denial rates on CPT Code 87635 claims rose after the PHE ended, as payers tightened medical necessity edits relaxed during the emergency. Knowing the specific denial codes lets your team route each denial to the right corrective action rather than resubmitting blindly.

• Wrong ICD-10 (CO-50 or CO-167): Using Z11.52 (screening) when the clinical record documents symptoms or exposure changes the coverage classification. Correct by swapping to U07.1 or Z20.822 and resubmitting with an updated ABN if cost-sharing shifted.
• 87635 + U0004 on the same claim (CO-97): Mutually exclusive codes; the lower-value code bundles into the higher. Void and resubmit with only one code. Determine the lab’s throughput capacity and pick the correct single code.
• Invalid POS (CO-5): POS 11 on a reference lab claim. Correct POS to 81 and resubmit. Confirm the performing lab’s address matches Box 32.
• Missing CLIA number (CO-16 with remark code MA120): Box 23 is blank or holds the ordering provider’s NPI. Supply the performing laboratory’s CLIA certificate number. If the CLIA certificate has lapsed, the test cannot be billed until recertification.
• QW modifier mismatch (CO-4): QW belongs only on a waived point-of-care test run under a certificate of waiver. Remove it from lab-based NAAT claims and resubmit. If the device was a waived rapid antigen system, the correct code is 87811, not 87635.
• Duplicate test same date of service (CO-18): Two 87635 claims from different providers on the same DOS. Confirm who performed the test, void the duplicate, and appeal with documentation showing separate specimens if both tests were clinically distinct.

Read the electronic remittance advice on every 87635 denial to confirm the adjustment and remark codes before correcting. Treat each code as a distinct root cause instead of resubmitting the same claim unchanged.

Documentation requirements for CPT 87635

CMS and commercial payers review 87635 claims for documentation adequacy, particularly orders placed without a clear clinical indication. The superbill for every 87635 encounter should capture these elements before the claim is submitted.

• Ordering provider NPI: The NPI of the clinician who ordered the test, not the performing lab’s NPI. It goes in Box 17b of the CMS-1500, separate from the performing lab’s details.
• Clinical indication: Symptoms (fever, cough, shortness of breath, loss of taste/smell), documented exposure history, or a specific pre-procedure screening protocol. Generic “COVID test ordered” is insufficient for audit defense.
• Test method explicitly stated: The lab report must identify the method as NAAT, RT-PCR, TMA, or comparable amplified probe technique. “Molecular test” is acceptable. “Rapid test” without further specification is not, and risks reclassification to 87811.
• Specimen type and collection date: Nasopharyngeal swab, anterior nasal swab, or saliva with the EUA-approved specimen type matched to the test device used.
• Performing lab CLIA number: Certificate number for the lab that processed the specimen, not where the result was reported. CLIA must be active (not expired or pending) on the date of service.
• Result report in the record: Final result (positive, negative, or indeterminate) with the reference laboratory’s name and director signature. Indeterminate results should be accompanied by clinical disposition notes.

Check your team’s documentation audit checklist against the CMS Medicare Claims Processing Manual (Pub. 100-04). The manual defines adequate supporting documentation for each lab claim type.

How practice management software reduces CPT 87635 billing errors

Each denial pattern above shows up on the claim before it leaves the practice. A blank Box 23, a POS 11 on a reference lab claim, or a U0004 line next to 87635 can all be caught at submission.

Pabau runs validation checks in the background every time you go to send a claim, so missing claim details get flagged before submission. In the US, its claims management software connects to Claim.MD to submit claims electronically, run real-time eligibility checks, and track claim status.

ERA remittances post back to the same dashboard. Your team sees a denied 87635 claim next to its adjustment code without logging in to each payer portal. That lets you correct and resend it the same day.

Reduce CPT 87635 denials before claims leave your system

Pabau runs validation checks in the background before you send a claim, then submits and tracks it through Claim.MD. Book a demo to see the billing workflow in action.

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Conclusion

Treat 87635 as the code you reach once the alternatives are ruled out. Antigen tests, multiplex panels and Medicare high-throughput runs each have their own code, and the lab report tells you which one applies.

The waiver question deserves a check on every claim. A waived point-of-care NAAT needs QW, and a lab-based RT-PCR must not carry it. With commercial cost-sharing back, a wrong call now lands on the patient’s bill as well as your denial queue.

Pabau checks each claim before it goes out and tracks its status through Claim.MD afterward. Book a demo to see how that fits your lab billing workflow.

Continue your research

Seeing repeated denials on COVID-related lab claims? Denial management in healthcare covers systematic approaches to tracking, categorizing, and resolving claim denials by root cause.

Want to understand the clearinghouse behind your 87635 submissions? Claim.MD clearinghouse explains how the integration connects Pabau to payers for eligibility checks and electronic claims.

Billing a flu antigen test alongside COVID-19 testing? CPT code 87804 covers the rapid influenza antigen code and when it applies instead of a NAAT.

Checking coverage before a COVID-19 test is ordered? Insurance eligibility verification walks through confirming benefits before the visit so cost-sharing does not surprise the patient.

Need a broader overview of the claim submission process? What is medical billing walks through the end-to-end revenue cycle from charge capture to payment posting.

Frequently asked questions