CPT code 81408 – Tier 2 molecular pathology sequencing, more than 50 exons

Key takeaways

CPT code 81408 covers DNA sequence analysis of more than 50 exons in a single gene. Multi-gene panels, exome sequencing and genome sequencing take other codes.

Genes the AMA names at Level 9 include NF1, DMD, RYR1 and RYR2. BRCA1 and BRCA2 testing has its own codes and never uses 81408.

Most commercial payers require prior authorization before the specimen is collected, and a missing authorization is one of the most preventable 81408 denials.

Pabau, the practice management platform we build, tracks prior authorization on the patient’s insurance case and warns when it is missing.

CPT code 81408: Official descriptor and Tier 2 classification

CPT code 81408 is the highest-complexity code in the AMA Tier 2 molecular pathology series. It covers DNA sequence analysis of more than 50 exons in a single gene.

The American Medical Association’s CPT code set organizes molecular pathology into two tiers, with nine complexity levels in Tier 2 (codes 81400 through 81408). Level 9 is the ceiling, reserved for the most demanding single-gene sequencing a CLIA-certified laboratory performs.

The descriptor’s “eg” signals that its example is illustrative rather than a complete list. A single gene whose full sequence analysis spans more than 50 exons may qualify when the clinical documentation supports it. The AMA gene list must not name it at a lower level.

What CPT code 81408 covers: Genes with more than 50 exons

The defining criterion is exon count within a single gene, not diagnostic category. A lab applies 81408 when one assay sequences more than 50 coding exons of one gene. The table below lists genes the AMA names at Level 9, with their approximate exon counts and the conditions they are tested for.

Genes move between levels when the AMA updates the list, so confirm each gene against the current Tier 2 list before billing. A common coding error is applying 81408 to BRCA1 or BRCA2 full sequencing. BRCA1 has about 24 exons and BRCA2 about 27, so neither meets the more-than-50-exon threshold. BRCA testing is reported with its own Tier 1 codes.

What CPT code 81408 does not cover: Exclusions and boundaries

Several test types look similar to 81408 but fall outside its scope. Picking the wrong code in either direction risks underpayment or an upcoding finding.

• 50 exons or fewer in a single gene: Use the matching lower Tier 2 code, from 81400 through 81407. Exon count and the AMA gene list set the level.
• Multi-gene panel tests: Panels with their own CPT codes are billed under those codes, not 81408. Examples include hereditary cancer panels (81432-81433) and cardiac panels (81439).
• Copy number variation analysis only: CNV detection without full sequence analysis is captured by array-based codes (81228, 81229), not molecular pathology sequencing codes.
• RNA-based assays: Transcriptome sequencing and RNA fusion panels use separate expression-analysis codes.
• Exome and genome sequencing: These are reported under 81415-81416 (exome) or 81425-81426 (genome), however many exons they cover. Whole-exome sequencing still uses 81415 or 81416 when the patient’s condition traces to a large gene.
• Unlisted molecular pathology: When no specific Tier 2 code applies, report 81479. It is the correct fallback, not an upgraded 81408.

How CPT 81408 compares to neighboring Tier 2 molecular pathology codes

The Tier 2 ladder sorts molecular pathology codes by analytical complexity, and exon count separates the sequence-analysis levels. The chart below shows where each exon band sits, with 81408 at the top.

The table maps the full ladder from 81400 to 81408, plus the unlisted code, so coders can confirm a selection before submitting.

Exon count is the default rule, but the AMA gene list overrides it at every sequencing level. A gene the list names at 81406 or 81407 is billed there, even when its sequenced exon count is higher. Check the current CPT codebook’s Tier 2 gene list before defaulting to 81408.

How the procedure is performed and what must be documented

Payers audit 81408 claims against the laboratory report. The report must show, not simply assert, that more than 50 exons were sequenced. These documentation elements decide whether a claim survives audit or is recouped.

1. Gene identity and exon count stated: The report must name the specific gene and confirm the number of coding exons sequenced. A report that says “full gene sequencing performed” without specifying the exon count is insufficient for 81408.
2. Sequencing methodology documented: Next-generation sequencing (NGS) or Sanger sequencing methodology must be described, including the sequencing platform and coverage depth.
3. Clinical indication linked to ordering physician’s note: The lab report must reference the clinical indication. The ordering provider’s note must document why the test was medically necessary. Family history, a prior inconclusive test, or matching clinical features all qualify.
4. Pathologist attestation: A board-eligible or board-certified molecular pathologist or laboratory director must sign out the report. Payers may ask for the pathologist’s name and credentials when they review the claim documentation.
5. CLIA certification of the performing lab: The laboratory NPI must map to a CLIA-certified facility. Claims from non-CLIA-certified labs are rejected regardless of documentation quality.

Clean claim submission for 81408 starts when the test is ordered, not when it is billed. When the ordering provider’s record captures the clinical indication at that point, the lab’s claim package can carry it forward.

Medicare coverage and reimbursement for CPT code 81408

Medicare covers CPT code 81408 under the Clinical Laboratory Fee Schedule (CLFS), administered by the Centers for Medicare and Medicaid Services. Coverage is not automatic. The claim must satisfy the Local Coverage Determination (LCD) of the laboratory’s Medicare Administrative Contractor (MAC).

Local Coverage Determinations governing 81408

LCDs specify which clinical indications Medicare covers for molecular pathology codes in a jurisdiction. The controlling LCD depends on where the laboratory is located, not where the patient lives. To find it, search the MAC’s coverage database with CPT code 81408 as the filter.

Palmetto GBA’s MolDX program manages molecular diagnostic LCDs for several MACs. It publishes clinical indication requirements that go beyond the AMA descriptor. Claims that meet the CPT definition but fall outside the LCD’s accepted indications are denied on medical necessity grounds.

Prior authorization requirements for CPT code 81408

Most commercial payers and many Medicare Advantage plans require prior authorization for genetic testing. Requirements vary by payer and plan year, so the guidance below reflects common patterns rather than universal rules.

• Traditional Medicare (Parts A and B): Generally does not require prior authorization for clinical laboratory tests, but LCD compliance is mandatory. Non-covered indications are denied on medical necessity grounds regardless of authorization status.
• Medicare Advantage plans: Many Medicare Advantage plans require prior authorization for high-cost genetic tests, including 81408. Requirements differ by plan, so verify them before the specimen is collected.
• Commercial payers (Aetna, UnitedHealthcare, Cigna, BCBS): Usually require prior authorization for Tier 2 molecular pathology codes at this complexity level. Collecting the specimen before authorization is approved is one of the most preventable denial causes.
• Medicaid: Varies by state. Some state programs pay for laboratory services directly, outside managed care. Others require authorization through a managed care organization, so check the specific state plan.

Prepare these documents before you submit the prior authorization request:

• The ordering provider’s clinical note documenting the specific clinical indication
• Relevant family history
• Prior genetic test results showing inconclusive or negative findings for lower-complexity assays
• The ICD-10 code supporting medical necessity
• The name of the gene to be sequenced, with confirmation that it exceeds 50 exons
• The name of the performing laboratory

ICD-10 codes that support medical necessity for CPT code 81408

Pairing CPT code 81408 with the wrong ICD-10 code is a frequent denial cause. The ICD-10 code must reflect the clinical indication that makes large-gene sequencing medically necessary. Avoid a general family history code when a more specific hereditary syndrome code exists.

Always cross-reference ICD-10 pairings against the controlling LCD for your jurisdiction. An ICD-10 code that is clinically appropriate may still be rejected if it is not on the LCD’s covered-indication list.

Why CPT 81408 claims get denied — and how to fix them

As a high-value code on the Clinical Laboratory Fee Schedule, 81408 draws frequent audits. The most common denial codes for molecular pathology cluster around a predictable set of documentation and eligibility failures. The table below maps each denial pattern to its corrective action.

Common coding mistakes to avoid with CPT 81408

• Upcoding from a lower-tier code without documentation: Upgrading from 81407 to 81408 on an assumed exon count creates recoupment risk. The lab report has to confirm that more than 50 exons were analyzed.
• Applying 81408 to multi-gene panels: Billing 81408 for the largest gene in a panel that has its own code is unbundling. Bill the panel code.
• Omitting modifier 59: Billing 81408 with another gene’s molecular pathology code on the same date may need modifier 59 or an X modifier. That applies when an NCCI edit bundles the two codes, and the modifier marks a distinct service.
• Confusing 81408 with exome codes: Whole-exome or clinical exome sequencing is never reported as 81408, even when the target gene has more than 50 exons.

How Pabau helps ordering practices prevent CPT 81408 denials

Many 81408 denials start at the ordering practice, not the lab. The lab bills the code, but it depends on the indication, ICD-10 code and authorization the practice recorded before collection. Strong denial management workflows connect the ordering provider, the laboratory and the billing team before the sample ships.

Pabau keeps those inputs on the patient record. Practices that switch on labs can order Quest tests from the record, and Labcorp orders placed in Labcorp Link sync results back automatically. Prior authorization sits on the patient’s insurance case with its code, dates and sessions, and Pabau warns when one is missing.

For the practice’s own insurance claims, Pabau’s claims software built for practices sends CMS-1500/837P claims through the Claim.MD clearinghouse. Claim.MD also supports eligibility checks before the visit. ERA remittances post back against the claim, so the medical billing compliance trail stays in one place.

Catch authorization problems before the sample ships

Pabau tracks prior authorization on each patient’s insurance case and warns when one is missing. See how it works for your practice.

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Conclusion

CPT code 81408 rewards discipline before submission more than most laboratory codes. The exon threshold, the AMA gene list and the LCD’s accepted indications settle most outcomes before a claim is built.

That puts the work at the order desk. Confirm the gene and its Tier 2 level, pair the most specific ICD-10 code, and secure authorization before collection. A slower order costs far less than a recouped high-value claim.

If your team is new to insurance claims, medical billing fundamentals walks through how a claim moves from order to payment. To see how Pabau tracks prior authorization and claims for your practice, book a demo.

Continue your research

Need help managing claim denials systematically? What is revenue cycle management explains how to structure your end-to-end billing workflow to reduce denial rates across all code types.

Want to understand clearinghouse claim processing? Medical claims clearinghouse guide covers how clearinghouses validate, route, and track claims before payer adjudication.

Looking to understand remittance and ERA reconciliation? Electronic remittance advice (ERA) explains how 835 files work and how to automate payment posting after molecular pathology claims are paid.

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