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    v1.0.30
    OpenPayerBilling CodesTherapeutic Drug AssaysCPT cpt-80184-phenobarbital-quantitative-assay
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    CPT 80184: Phenobarbital Quantitation in Patient Specimen

    CPT code 80184 describes a clinical toxicology assay where a laboratory analyst performs the technical procedure to quantitate the concentration of phenobarbital, an anticonvulsant medication, in a patient specimen; the service type is therapeutic drug monitoring / quantitative laboratory testing and the typical site of service is a clinical laboratory or hospital laboratory (specimen received and processed in a lab setting).

    For related coverage guidance, see recent payer policy updates: Long-Acting Injectable Antiretroviral Agents for HIV, B-Hemolytic Streptococcus Testing, Human Immunodeficiency Virus (HIV) — Coverage Criteria for Testing and Resistance Assays.

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    Table of contents

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    Clinical & Coding Specifications

    Clinical Context

    A 28-year-old patient with a history of generalized tonic-clonic seizures presents for routine therapeutic drug monitoring. The patient is prescribed phenobarbital and reports variable adherence and recent breakthrough seizures. A blood specimen is collected at an outpatient laboratory draw station and sent to the hospital clinical chemistry/toxicology laboratory. The lab analyst performs a quantitative assay to determine serum phenobarbital concentration (CPT 80184) to assess therapeutic level, toxicity risk, and medication adherence.

    Typical workflow: a clinician orders a serum phenobarbital level with an ICD-10 diagnosis supporting anticonvulsant monitoring; the phlebotomist obtains the specimen; the specimen is accessioned and routed to the clinical chemistry or toxicology section; a medical laboratory scientist or technician runs the quantitative assay (immunoassay or chromatographic method) and verifies analytic quality control; results are reviewed and released to the ordering provider; the clinician interprets results for dose adjustment or further testing.

    Related CPT Codes

    CPT CodeDescriptionRelationship to This Procedure
    80184Phenobarbital; quantification, e.g., therapeutic drug monitoringPrimary technical laboratory assay to quantify serum phenobarbital concentration.
    80053Comprehensive metabolic panel; 14 testsOften ordered concurrently to assess electrolytes, renal and hepatic function that affect phenobarbital metabolism.
    80307Specimen drug testing, qualitative; multiple drug class screeningMay be performed alongside to screen for other substances or co-ingestants in toxicity evaluation.
    82570Drug assay, presumptive, any number of drug classes; qualitativeUsed when initial screening for multiple drugs is needed prior to or in addition to specific quantification.
    80160Phenobarbital; presumptive immunoassay, qualitativeA screening immunoassay may precede quantitative 80184 to detect presence before running a confirmatory quantitation.

    Related Modifiers

    7 rows

    ModifierDescriptionWhen to Use
    26Modifier 26 (Professional Component) identifies and bills only the professional portion of a split service — the physician’s interpretation, report, and medical judgment — when the technical…- Use CPT Modifier -26 when you are billing only the professional component (PC) of a split‑bill eligible service—i.e., you performed the physician interpretation, medical judgment and prepared a…
    90Modifier ‑90 (Reference/Outside Laboratory) indicates that a laboratory test was performed by an entity other than the treating or reporting provider. The American Medical Association defines…- Use CPT modifier -90 when a laboratory test is performed by an outside/reference laboratory (an entity other than the treating or reporting physician or qualified professional) and the claim needs…
    91Modifier 91 — “Repeat Clinical Diagnostic Laboratory Test” — is appended when the exact same CPT laboratory test is performed more than once for the same patient on the same day because serial,…- Use modifier 91 when the exact same CPT laboratory test is performed more than once on the same patient on the same date because serial or repeated testing is medically necessary to monitor…
    59Modifier 59 indicates a distinct procedural service when two procedures that are not normally billed together are clinically and procedurally separate. The CPT definition (as reiterated by CMS)…- Use modifier -59 to report a distinct procedural service when documentation supports that the procedure reported is not normally billed together with another service on the same day because of a…
    52Modifier ‑52 (Reduced Services) indicates that a service or procedure was partially reduced or omitted at the provider’s discretion, allowing reporting of the basic procedure number with a qualifier…- Use modifier -52 when a physician or qualified health professional electively reduces or omits part of a procedure or service (for example, performing fewer required views or omitting a portion of…
    53Modifier 53 (Discontinued Procedure) signals that a surgical or diagnostic service was begun by the physician but terminated because of extenuating circumstances that threatened the patient’s…- Use modifier -53 when a physician/qualified healthcare professional has started a surgical or diagnostic procedure (e.g., anesthesia administered, incision or scope insertion) and then discontinues…
    23Modifier -23 (Unusual Anesthesia) is used on anesthesia service CPT codes when a procedure that normally requires no anesthesia or only local anesthesia must be performed under general anesthesia…- Use modifier -23 only on anesthesia CPT codes (00100–01999) when a procedure that normally requires no anesthesia or only local anesthesia must be performed under general anesthesia because of…

    Related Provider Taxonomies

    8 rows

    Taxonomy Code
    1223G0001X
    207R00000X
    208D00000X
    332G00000X
    111NT0100X
    207RA0000X
    2279S1500X
    2472V0600X

    Related ICD-10-CM Codes

    26 rows

    ICD-10-CM CodeDescription
    F07.81Postconcussional syndrome
    F11.20Opioid dependence, uncomplicated
    F13.20Sedative, hypnotic or anxiolytic dependence, uncomplicated
    F19.20Other psychoactive substance dependence, uncomplicated
    F32.9Major depressive disorder, single episode, unspecified
    F33.1Major depressive disorder, recurrent, moderate
    F41.1Generalized anxiety disorder
    F90.9Attention-deficit hyperactivity disorder, unspecified type
    G25.0Essential tremor
    G31.84Mild cognitive impairment of uncertain or unknown etiology

    Showing 1–10 of 26

    Related Payer Policy Updates

    Specialty: Infectious Disease1 / 3

    10 rows

    PolicyPayerEffective Date
    Long-Acting Injectable Antiretroviral Agents for HIVColorado Rocky Mountain Health Plans2026-10-01
    B-Hemolytic Streptococcus TestingOscar Health2026-10-01
    Human Immunodeficiency Virus (HIV) — Coverage Criteria for Testing and Resistance AssaysOscar Health2026-10-01
    Hepatitis Testing (A, B, C, D) Coverage CriteriaOscar Health2026-10-01
    Lyme Disease Testing Coverage CriteriaOscar Health2026-10-01
    Pathogen Panel TestingOscar Health2026-10-01
    Diagnostic Testing of Common Sexually Transmitted InfectionsOscar Health2026-10-01
    Testing for Vector-Borne InfectionsOscar Health2026-10-01
    Testing for Diagnosis of Active or Latent TuberculosisOscar Health2026-10-01
    Coronavirus Testing in the Outpatient SettingOscar Health2026-10-01

    Related Codes

    CPT-80143-ACETAMINOPHEN-QUANTITATIVE-SERUM-ASSAY

    CPT 80143: Acetaminophen Quantitative Assay

    CPT-80145-ADALIMUMAB-LEVEL-ASSAY-THERAPEUTIC-DRUG-MONITORING

    CPT 80145: Adalimumab Quantitative Drug Level Assay

    CPT-80150-AMIKACIN-QUANTITATIVE-ASSAY-THERAPEUTIC-DRUG-MONITORING

    CPT 80150: Amikacin Quantitative Serum Level

    CPT-80151-AMIODARONE-QUANTITATIVE-SERUM-ASSAY

    CPT 80151: Amiodarone Quantitative Drug Level Assay

    CPT-80155-CAFFEINE-LEVEL-TESTING

    CPT 80155: Caffeine Level Quantification

    CPT-80156-CARBAMAZEPINE-TOTAL-LEVEL-LAB-ASSAY

    CPT 80156: Carbamazepine Total Level (Serum)

    CPT-80157-FREE-CARBAMAZEPINE-ASSAY

    CPT 80157: Free Carbamazepine Quantitative Assay

    CPT-80158-CYCLOSPORINE-QUANTITATIVE-ASSAY-LAB

    CPT 80158: Cyclosporine Quantitation, Laboratory

    CPT-80159-CLOZAPINE-LEVEL-ASSAY-THERAPEUTIC-DRUG-MONITORING

    CPT 80159: Clozapine Level Measurement

    CPT-80161-CARBAMAZEPINE-EPOXIDE-QUANTITATIVE-ASSAY

    CPT 80161: Carbamazepine 10,11-Epoxide Level, Quantitative

    Showing 1–10 of 87

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    Frequently Asked Questions

    References

    1. 1.CPT® Codes and Descriptions. AAPC. Retrieved Aug 11, 2026.Maintains the CPT code set's official descriptions and guidelines, licensed from the American Medical Association, used as the definitional source for CPT codes on this page.
    2. 2.HCPCS Quarterly Update. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's quarterly release of HCPCS Level II codes and short/long descriptors, the source for HCPCS code definitions and update history.
    3. 3.ICD-10-CM Full Code List. Centers for Medicare & Medicaid Services (CMS). Retrieved Aug 11, 2026.CMS's complete ICD-10-CM diagnosis code list, used to cross-reference diagnosis codes associated with this procedure or service.
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