Summary & Overview
CPT 0422U: Guardant360Response™ ctDNA NGS Assay for Treatment Response
CPT code 0422U designates Guardant Health Inc.'s Guardant360Response™, a proprietary next-generation sequencing (NGS) circulating tumor DNA (ctDNA) assay that quantifies change from a prior baseline test to evaluate response to anticancer therapy. As a PLA code, 0422U is uniquely tied to a single manufacturer's test and is used when the laboratory reports a quantitative comparison with the baseline test 0326U, including specific alterations when present. Nationally, PLA codes like 0422U matter because they standardize billing for novel, lab-specific molecular diagnostics that inform treatment response decisions and precision oncology pathways.
Key payers addressed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the code's clinical purpose, expected service setting, and payer landscape. The publication summarizes benchmark considerations, coding context for PLA tests, and clinical utility in monitoring solid-organ neoplasm response to systemic anticancer therapies. Data limitations: information on modifiers beyond commonly used modifiers, associated taxonomies, and specific ICD-10 pairings are not available in the input.
Billing Code Overview
CPT code 0422U is a Proprietary Laboratory Analyses (PLA) code specific to Guardant Health Inc.'s Guardant360Response™ test. The assay is a next-generation sequencing (NGS) targeted panel that analyzes cell-free circulating tumor DNA (ctDNA) from a blood specimen to evaluate genes associated with solid-organ neoplasms. The code applies only to this single, manufacturer-specific test and reports a quantitative change from an earlier baseline test, 0326U, using an algorithmic comparison to assess patient response to anticancer therapy.
Service type: Laboratory — Proprietary NGS-based circulating tumor DNA (ctDNA) response assay
Typical site of service: Clinical laboratory or outpatient blood-draw setting (phlebotomy) with specimen sent to the performing laboratory for NGS analysis
Clinical & Coding Specifications
Clinical Context
A typical patient is a 62-year-old with metastatic non-small cell lung cancer (NSCLC) receiving targeted therapy. The patient had an initial Guardant360Response™ baseline blood test (0326U) at treatment start. After two to three treatment cycles or at clinical suspicion of progression, the oncology team orders Guardant360Response™ (0422U) to evaluate quantitative changes in circulating tumor DNA (ctDNA) compared with the baseline. A peripheral blood sample is drawn in the outpatient oncology clinic or an ambulatory phlebotomy site and sent to the performing laboratory. The laboratory performs next-generation sequencing (NGS) targeted analysis of cell-free DNA, applies the proprietary algorithm to compare to baseline results, and issues a report quantifying change in tumor fraction and listing specific genomic alterations if present. The oncology clinician reviews the report to inform assessment of treatment response, consider imaging correlation, and decide on therapy continuation, modification, or additional diagnostic evaluation.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
00 | Unspecified modifier (used by some carriers as default) | Rarely used; follow payer guidance if a neutral modifier is required by claim form. |
| Increased procedural services | Use when the laboratory documents a substantially greater level of work or complexity beyond typical assay processing, and payer allows modifier for lab services.