Summary & Overview

CPT 0605U: Tryptase Gene Copy Number Analysis by dPCR

CPT code 0605U designates a Proprietary Laboratory Analyses (PLA) molecular test: Tryptase Gene Copy Number Analysis by digital PCR from Virant Diagnostics Inc. The assay quantifies copies of the TPSAB1 gene from whole blood and reports genotype-specific alpha tryptase copy number with algorithmic classification as normal or abnormal. As a PLA code, 0605U applies to a single, manufacturer-specific test and is relevant to precision diagnostics, hereditary tryptase-associated conditions, and downstream clinical management considerations.

Key national payers in scope include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a national-level briefing on the clinical purpose of the test, payer coverage landscape, and the policy and coding context for a PLA molecular diagnostic. The publication outlines common billing considerations for laboratory genetic tests, highlights how PLA designation affects coding and uniqueness of the service, and summarizes expected sites of service and specimen type. Data not available in the input will be noted where applicable.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicare0605UCPTProprietary Laboratory Analysesmolecular diagnosticsdigital PCRTPSAB1tryptasegenetic testinglaboratory

Billing Code Overview

CPT code 0605U is a Proprietary Laboratory Analyses (PLA) code for Tryptase Gene Copy Number Analysis by digital PCR (dPCR) performed by Virant Diagnostics Inc. The test determines the copy number of the TPSAB1 gene using digital polymerase chain reaction on DNA extracted from whole blood. Results include genotype-specific interpretation of alpha tryptase copy number and are classified as normal or abnormal using a provided algorithm.

Service type: Laboratory genetic testing — molecular diagnostic (digital PCR) for gene copy number analysis

Typical site of service: Clinical laboratory or reference diagnostic laboratory, with specimen collection from whole blood

Clinical & Coding Specifications

Clinical Context

A typical patient is an adult referred by an allergist or immunologist for evaluation of suspected hereditary alpha tryptasemia after clinical features such as recurrent idiopathic anaphylaxis, unexplained systemic mast cell activation symptoms (flushing, abdominal pain, diarrhea, urticaria), elevated baseline serum tryptase, or a family history of elevated tryptase. The ordering clinician collects whole blood in EDTA and sends the specimen to Virant Diagnostics Inc. for 0605U Tryptase Gene Copy Number Analysis by digital PCR. The laboratory performs dPCR to quantify TPSAB1 alpha-tryptase copy number; results are reported as genotype-specific copy number with algorithmic classification as normal or abnormal. The report is reviewed by the ordering clinician to integrate genetic results with clinical findings for diagnostic clarification and family counseling. Typical site of service is an outpatient clinic, specialty allergy/immunology office, or a reference clinical laboratory; specimen collection occurs in a phlebotomy clinic or outpatient lab service.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing separate professional interpretation of the laboratory report (rare for PLA codes that are fully bundled to the performing lab).

Taxonomy Code	Specialty	Notes
`208Z00000X`	Allergy & Immunology	Clinicians who commonly order TPSAB1 testing for suspected hereditary alpha tryptasemia.
`207K00000X`	Clinical Pathology	Pathologists and laboratory medicine specialists overseeing test validation and result interpretation.
`208000000X`	Pediatrics	Pediatric allergists/immunologists may order testing for children with elevated tryptase or familial symptoms.
`207L00000X`	Clinical Molecular Genetics	Laboratory geneticists who develop and perform dPCR-based copy number assays.
`207R00000X`	Diagnostic Radiology (Laboratory Management)	Laboratory directors in some organizations with combined diagnostic oversight roles.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`D89.89`	Other specified disorders involving the immune mechanism, not elsewhere classified	Used when evaluating unexplained mast cell activation or immune-mediated symptoms prompting TPSAB1 testing.
`T78.2`	Anaphylactic shock, unspecified	May be listed when patients have recurrent anaphylaxis under evaluation for hereditary alpha tryptasemia.
`R78.0`	Hypergammaglobulinemia, unspecified	Occasionally used in workups of systemic symptoms with immune markers; less specific but part of differential testing.
`R21`	Rash and other nonspecific skin eruption	Skin manifestations like urticaria can prompt consideration of mast cell disorders and gene testing.
`R10.9`	Abdominal pain, unspecified	Recurrent unexplained abdominal pain from mast cell mediator release can be an indication for TPSAB1 analysis.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`0605U`	Tryptase Gene Copy Number Analysis by dPCR (Virant Diagnostics Inc.)	Primary proprietary laboratory analyte; report of TPSAB1 alpha tryptase copy number used for diagnosis of hereditary alpha tryptasemia.
`36415`	Collection of venous blood by venipuncture	Typically performed prior to sending whole blood specimen to the reference lab for `0605U` testing.
`99000`	Handling and/or conveyance of specimen to reference lab (clinical laboratory fee)	Used by some facilities to bill specimen handling and shipping costs when sending to an outside lab.
`0000U`	(Placeholder PLA example)	Other PLA tests for related molecular assays may be used in parallel in specialized diagnostic workflows (use specific PLA codes for actual tests).
`81162`	BRCA1/BRCA2 analysis (example of high-complexity molecular testing)	Represents similar high-complexity molecular reporting workflows; listed to illustrate molecular testing context rather than direct clinical overlap.