Author: Manikandan (Mani) | Senior Medical Billing Specialist, 10+ Years in RCM
Published: August 2026 | Last Updated: August 2026
Read time: 8 minutes
Why is CPT 87798 being denied for 13 units?
CPT 87798 is being denied for 13 units because payers have moved this code into active enforcement in 2026, and 13 units billed on a single date of service trips every automated edit that enforcement triggers. This is not payer variability. It is systematic pre-adjudication review that started ramping up from early 2026 across Medicare Administrative Contractors including Novitas Solutions, NGS Medicare, and First Coast Service Options.
Three problems are colliding on your claim at once. First, 87798 is a “not otherwise specified” catch-all code, and payers now require coding specificity — each unit must represent an organism with no existing specific CPT code, documented individually. Second, all the codes on your panel fall under the same clinical intended use, which is respiratory pathogen detection, and CMS Article A58720 limits how many tests payers will cover for the same intended use on a single date of service. Third, when the total pathogen count on a claim reaches 6 or more, payers expect a panel code rather than individual unbundled codes. Your claim exceeds all three thresholds simultaneously, which is why all 13 units are being denied rather than just some of them.
What does each code in your panel actually mean?
Understanding what each code represents matters here because the combination — not just the 87798 count — is what the payer’s adjudication system is reading as a problem.
| CPT Code | What it tests | Units | Issue |
|---|---|---|---|
| 87481 | Candida species, amplified probe | x5 | Five Candida species on the same DOS raises the same-intended-use flag immediately |
| 87500 | Vancomycin resistance gene detection | x1 | Generally billable separately when distinct clinical indication documented |
| 87640-XU | Staphylococcus aureus, amplified probe | x1 | XU modifier indicates unusual non-overlapping service — correct approach |
| 87641 | MRSA detection | x1 | Separate from 87640 but payers often bundle these without XU documentation |
| 87651 | Streptococcus A, amplified probe | x1 | Specific code exists — generally allowable with correct ICD-10 |
| 87653 | Streptococcus B, amplified probe | x1 | Specific code exists — generally allowable with correct ICD-10 |
| 87798 | Infectious agent NOS, amplified probe, each organism | x13 | 13 NOS units without organism-level documentation triggers enforcement edits |
When a payer looks at this claim, their system sees 22 total units of molecular pathogen detection across 7 code lines, all on the same date of service. The adjudication engine treats this as one respiratory infectious disease workup that has been unbundled into individual components — which is exactly what CMS Article A58720 prohibits.
What is the “same intended use” rule and why does it matter here?
The same intended use rule comes from CMS Article A58720, which governs molecular syndromic panel billing across Medicare and many commercial payer policies. It defines “same intended use” as tests ordered for the same clinical purpose, even when they target different pathogens or organisms. Every code on your claim — the Candida codes, the Staph codes, the Strep codes, and all 13 NOS units — is targeting infectious pathogen identification from the same specimen on the same date. They all share one intended use.
Under this rule, CMS treats a collection of individually unbundled pathogen tests ordered for the same clinical purpose as a single panel service. Billing them as separate line items does not change how the payer adjudicates them. A58720 states this plainly: a panel cannot be unbundled and billed as individual components regardless of the fact that the test reports multiple individual pathogens. The rule does allow separate billing for organisms not included in any panel code, but that exception applies to a small number of additional targets — not to 13 additional NOS units stacked on top of an already substantial panel.
The practical consequence for your claim is that payers are not evaluating each of your 87798 units individually. They are looking at the totality of the claim, seeing a large-scale respiratory pathogen workup, and denying the unbundled representation of it.
Does billing 87798 on a separate claim fix the denial?
No. Billing the 13 units of 87798 on a separate claim does not resolve the denial, and attempting it creates additional compliance risk. Payers adjudicate by date of service, not by claim number. When the same member has two claims on the same date of service for molecular pathogen testing from the same specimen, payers cross-reference them and apply the same same-intended-use analysis. The denial follows the date of service, not the claim form.
Split billing for the same date of service also raises a pattern flag that can escalate the account into prepayment review or audit. Several labs have reported that after attempting to separate 87798 units onto a second claim, their accounts were flagged for broader utilization review. The correct approach is to fix the claim structure itself, not to change which form the codes appear on.
The one scenario where truly separate billing is legitimate is if some of your 87798 units represent organisms tested from a different specimen type, for a different clinical indication, with a distinct ICD-10 code that has no connection to the respiratory panel. That requires specific documentation and cannot be assumed based on how the current panel is structured.
What are the correct codes to use instead?
The right approach depends on two things: what the 13 organisms tested under 87798 actually are, and what your payer covers. Work through these options in order.
Step 1: Identify each of the 13 organisms
Go through your lab report and name every organism currently billed under 87798. For each one, check the current AMA CPT code set for a specific code. The CPT code set expands regularly and organisms that required 87798 two years ago may now have their own code. Any organism with a specific code should be re-coded immediately. This alone may reduce your 87798 unit count significantly.
Step 2: Evaluate panel codes for commercial payers
If your total pathogen count across the entire panel reaches 6 to 11 targets, consider CPT 87632 (respiratory virus panel, 6 to 11 targets). If it reaches 12 to 25 targets, consider CPT 87633 (respiratory virus panel, 12 to 25 targets). These are single-unit codes that represent the whole panel as one service.
One critical restriction: CMS explicitly lists 87633 as non-covered for traditional Medicare. If you are billing Medicare fee-for-service, 87633 will be denied regardless of clinical justification. Verify your specific payer’s policy before using either panel code. Some Medicare Advantage plans and commercial payers do cover these codes and they are the correct path for those payers.
Step 3: Check for PLA codes
If you are running a named proprietary assay or an FDA-cleared panel, a Proprietary Laboratory Analysis code may exist that is specific to your test platform. PLA codes carry stronger payer recognition than 87798 for the same organisms. Check the AMA PLA database against the specific test name and manufacturer.
Step 4: MolDx Z-code pathway for Medicare
If you are in a MolDx jurisdiction and your test does not map cleanly to any existing covered code, the correct pathway is a Z-code submission with a Technical Assessment from Palmetto GBA. This is the formal route for laboratory-developed tests and novel assays under Medicare. Skipping this step and billing 87798 in volume without a TA on file is what generates the enforcement denials you are seeing.
How do you build a winning appeal for this denial?
Appeals for 87798 multi-unit denials succeed when they do one specific thing: document each unit individually, not the panel as a whole. A general appeal letter explaining that the tests were medically necessary will not move these denials. Payers need organism-level specificity.
Your appeal packet should contain five elements.
An organism identification list that names every one of the 13 organisms tested under 87798, confirms that no specific CPT code existed for each at the time of the test, and references the CPT code set edition you checked. This list needs to be specific enough that a payer medical reviewer can verify it independently.
Physician documentation that shows why each organism was clinically indicated for this patient on this date. This means the ordering physician’s notes need to address the patient’s specific presentation, risk factors, and treatment decisions — not a templated panel order form that lists organisms without clinical context.
The full lab report showing the amplified probe technique used for each organism and the result for each. CMS Article A58720 specifically requires documentation of the technique, and many payer appeals reviewers check for it by name.
A copy of the applicable Local Coverage Determination with the specific coverage criteria that support your organisms highlighted and referenced in your letter.
The A58720 unbundling exception language. Cite the exact passage that permits separate billing for organisms not included in a panel code, and map each of your 13 organisms to that exception with specific documentation showing why the panel codes do not cover them.
Sample appeal opening:
“We are appealing the denial of CPT 87798 x13 for [MEMBER ID] on [DATE OF SERVICE]. Each of the 13 units represents a distinct infectious organism for which no specific CPT code exists as documented in the enclosed organism identification list. Medical necessity for each organism is supported by the enclosed physician documentation and lab report. We respectfully request reconsideration under the individual pathogen testing exception in CMS Article A58720.”
What should you check before resubmitting?
| Check | What to do |
|---|---|
| Name all 13 organisms under 87798 | Confirm no specific CPT code exists for each one in the current code set |
| Count total panel targets | If 12 or more, evaluate 87633 for commercial payers only — not Medicare |
| Check 87481 x5 documentation | Five Candida species requires distinct clinical justification per species |
| Verify XU modifier on 87640 | Documentation must support the unusual non-overlapping service claim |
| Confirm MolDx jurisdiction | If Medicare in a MolDx state, Z-code and Technical Assessment may be required before billing |
| Check PLA codes for your assay | Search the AMA PLA database by test platform and manufacturer name |
| Match ICD-10 codes to each organism | Every ICD-10 must support medical necessity for the specific organism, not just a general respiratory infection code |
| Run an internal audit | Review 6 months of 87798 claims to identify your full exposure before resubmitting |
| Separate claim approach | Do not attempt split billing by date of service — it escalates rather than resolves the denial |
Key takeaways
- CPT 87798 denials for 13 units in 2026 are the result of active payer enforcement, not a coverage policy change. Payers have moved this code into systematic pre-adjudication review and 13 units on a single date of service is a clear enforcement trigger.
- The same intended use rule under CMS Article A58720 is the legal basis for these denials. All codes on your panel share one clinical purpose — respiratory pathogen identification — and payers treat the whole claim as one bundled service.
- Billing 87798 on a separate claim does not fix the denial. Payers adjudicate by date of service, and split billing raises additional compliance flags.
- The correct first step is naming all 13 organisms and checking whether specific CPT codes now exist for any of them. Reducing your 87798 unit count by recoding where specific codes exist is the most direct fix.
- For commercial payers with panels of 12 or more targets, evaluate CPT 87633. Do not use 87633 for traditional Medicare — it is explicitly non-covered by CMS.
- Winning appeals require organism-level documentation for each unit, not a general medical necessity letter. Name each organism, confirm no specific code exists, and cite the A58720 unbundling exception by name.
- Run an internal audit of your 87798 billing pattern across the past 6 months before resubmitting. The enforcement pattern affecting your 13 units likely affects other claims in your account as well.
Manikandan is a Revenue Cycle Management (RCM) specialist with over 10 years of hands-on experience in US healthcare billing. He has worked extensively with commercial payers, Medicare, and Medicaid across multiple specialties including surgery, orthopedics, and radiology. Manikandan founded Medical Billing 101 to provide free, accurate denial code guides, CPT coding references, and Medicare billing resources for US medical billing professionals.