CPT 84035
Global XXXAssay of phenylketones
This code does not have a national work RVU on the current Physician Fee Schedule. Pricing may be carrier-determined, non-covered, or tracked via a separate methodology.
CPT 84035 Billing & Documentation Guide
CPT code 84035 (Assay of phenylketones) is classified under Pathology/Lab with a global period indicator of XXX. This code uses the No national RVU payment methodology rather than standard RVU-based Physician Fee Schedule pricing. Refer to the methodology notice above for billing implications.
When billing 84035, ensure documentation supports medical necessity and the specific components required for the code's level of service. For E/M codes, document MDM (medical decision-making) elements: problems addressed, data reviewed, and risk. For procedural codes, document the indication, technique, and any complications. Always verify NCCI edits before bundling 84035 with related codes; this code has 1 PTP bundling relationships on file (see table below).
Payment Status & Global Period
Statutory exclusion
No global period (E/M and other non-procedural services)
MUE Limit (Medically Unlikely Edits)
Submitting more than 1 units of 84035 for the same patient on the same date triggers automatic line denial unless an appropriate modifier and supporting documentation justify the higher quantity.
NCCI Bundling Edits, CPT 84035
Procedure-to-procedure (PTP) edits. If you bill any of these codes with 84035 on the same date of service, review the modifier indicator and payer policy before submission.
| Partner Code | Relationship | Modifier Allowed | Rationale |
|---|---|---|---|
| 96523 | Column 1 (primary), can be billed with modifier | No | CPT Manual or CMS manual coding instruction |
Frequently Asked Questions, CPT 84035
What does CPT code 84035 mean? +
CPT code 84035 represents: Assay of phenylketones. It's in the Pathology/Lab category with a global period of XXX.
What is the Medicare reimbursement for CPT 84035? +
This code does not have a national work RVU on the current Physician Fee Schedule. Pricing may be carrier-determined, non-covered, or tracked via a separate methodology.
What modifiers can I use with CPT 84035? +
Pathology and laboratory use modifier 90 (reference/outside lab), 91 (repeat clinical diagnostic test same day), 92 (alternative laboratory platform), and QW (CLIA waived test). Surgical pathology splits between 26 and TC where applicable.
What bundling edits apply to CPT 84035? +
This code has 1 NCCI PTP bundling relationships. See the NCCI Bundling section below for full list.
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Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on April 17, 2026.
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