Summary & Overview
CPT 82379: Total and Free Carnitine Measurement
CPT code 82379 represents measurement of both total and free carnitine in serum, plasma, urine, or tissue. Carnitine testing identifies abnormalities in cellular fatty acid transport and mitochondrial fuel utilization and is commonly used to follow up positive newborn screening results or to evaluate suspected metabolic disorders. Nationally, this lab test supports diagnostic pathways for inherited metabolic conditions and influences clinical management in neonates and patients with muscle weakness or hypoketotic hypoglycemia.
Key payers in the coverage landscape include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of the clinical context for ordering carnitine testing, typical sites where the service is delivered, and the common billing environment for laboratory biochemical analyses. The publication summarizes benchmarks and payer coverage patterns where available, outlines relevant coding considerations for the laboratory service line, and highlights policy updates that affect laboratory authorization and medical necessity evaluation. The material is intended to support billing, coding, and policy teams, as well as clinicians seeking concise context for CPT code 82379.
Billing Code Overview
CPT code 82379 describes laboratory measurement of total and free carnitine in serum, plasma, urine, or tissue specimens. Total carnitine comprises both free carnitine and acylcarnitines, which are carriers that transport long‑chain fatty acids into mitochondria for use as cellular fuel. This testing is clinically relevant for evaluation of suspected carnitine deficiency or disorders of fatty acid oxidation and is often ordered after a newborn screen returns a positive blood spot result.
Service Type: Clinical laboratory biochemical analysis
Typical Site of Service: Clinical laboratory, hospital lab, reference laboratory, or specialty testing facility
Clinical & Coding Specifications
Clinical Context
A newborn infant born at a community hospital has a positive newborn screening blood spot for possible carnitine deficiency. The pediatrician orders quantitative serum testing for both total and free carnitine to confirm the screen. The infant is brought to the hospital outpatient laboratory or the hospital clinical chemistry laboratory where a phlebotomy technician collects a serum or plasma specimen. The specimen is sent to the biochemical genetics or hospital chemistry lab where a laboratory analyst performs analysis for total and free carnitine (CPT 82379). Results are reviewed by the pediatrician or a metabolic specialist; abnormal results prompt confirmatory testing, metabolic consult, nutritional counseling, and potential initiation of carnitine supplementation. Typical workflow steps: order placement in the electronic health record, specimen collection (serum, plasma, or urine), specimen processing and testing in the lab, result verification by laboratory personnel, and clinician review with documentation in the infant’s chart. Typical sites of service include hospital outpatient laboratory, ambulatory clinic laboratory, reference laboratory, and inpatient hospital laboratory when performed on hospitalized infants or patients under metabolic workup.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional Component | Use when billing only the physician or pathologist interpretation component and the laboratory component is billed by another entity. |
TC | Technical Component | Use when billing only the laboratory technical component (equipment, technician, reagents) and a separate professional interpretation is not billed. |
91 | Repeat Clinical Diagnostic Laboratory Test | Use when a repeat test is performed on the same patient on the same day for confirmation or to verify a critical value. |
90 | Reference (Outside) Laboratory | Use when the testing was performed by an outside/reference laboratory and billed through the ordering facility as an outsourced service. |
59 | Distinct Procedural Service | Use when another distinct test or procedure is performed the same day and documentation supports reporting separately. |
52 | Reduced Services | Use when a reduced service is performed relative to the full description (rare for standardized lab panels). |
53 | Discontinued Procedure | Use when specimen collection/testing was started but discontinued for documented medical reasons. |
22 | Increased Procedural Services | Use when work or resources required are substantially greater than typical and documentation supports the increased complexity. |
78 | Unplanned Return to the Operating/Procedure Room by Same Physician Following Initial Procedure for a Related Procedure During the Postoperative Period | Generally not applicable to routine lab testing but included when a related procedural return requires repeat intraoperative testing. |
90 | Reference (Outside) Laboratory | Use when an outside commercial laboratory performed the technical component and the report is submitted by the ordering provider. |
| Taxonomy Code | Specialty | Notes |
|---|---|---|
| 2080S0200X | Clinical Pathology | Specialists who interpret metabolic and biochemical laboratory results. |
| 2080P0202X | Clinical Biochemical Genetics | Providers involved in metabolic disorder evaluation and follow-up. |
| 207RC0000X | Pediatric Pathology | Pathologists who support neonatal and pediatric laboratory testing. |
| 2085R0202X | Pediatrics | Pediatricians ordering and managing newborn metabolic screening follow-up. |
| 207L00000X | Clinical Laboratory Science/Medical Technology | Laboratory directors and technologists who perform and oversee testing. |
Related Diagnoses
| ICD-10 Code | Description | Clinical Relevance |
|---|---|---|
E71.320 | Disorder of branched-chain amino-acid metabolism, unspecified | Metabolic disorders can present with abnormal carnitine levels; evaluation often includes carnitine testing. |
E71.39 | Other disorders of branched-chain amino-acid metabolism | Similar metabolic conditions where carnitine assessment supports diagnosis and management. |
E71.40 | Disorders of fatty-acid metabolism, unspecified | Primary disorders of fatty-acid oxidation commonly evaluated with free and total carnitine measurements. |
E71.41 | Long-chain fatty-acid oxidation disorders | Directly related to carnitine function; testing assesses substrate transport into mitochondria. |
E78.2 | Mixed hyperlipidemia | Secondary metabolic testing including carnitine may be considered in broader metabolic evaluations. |
Related CPT Codes
| CPT Code | Description | Relationship to This Procedure |
|---|---|---|
81025 | Urinalysis by dip stick or tablet reagent for bilirubin, glucose, hemoglobin, ketones, leukocytes, nitrite, pH, protein, specific gravity, urobilinogen, any number of these tests; non-automated, with microscopy | Performed when urine specimens are collected in parallel to evaluate renal function or to obtain urine specimen for carnitine measurement. |
82043 | Assay of carnitine (free and total) — note: alternative lab codes may be used depending on methodology | Related biochemical assays and alternate lab code usage; used when reporting specific carnitine analyses depending on laboratory billing practice. |
82607 | Assay of serum ammonia | Often performed alongside carnitine testing in suspected metabolic disorders to assess for hyperammonemia. |
83970 | Assay of amino acids, quantitative, plasma (e.g., amino acid profile) | Performed as part of a metabolic workup for inborn errors of metabolism that can accompany abnormal carnitine levels. |
81000 | Urinalysis, by dipstick or tablet reagent; automated, without microscopy | Used when automated urinalysis is obtained with urine specimens submitted for metabolic evaluation. |
80053 | Comprehensive metabolic panel (CMP) | Often ordered concurrently to assess overall metabolic status and organ function during evaluation of possible metabolic disorders. |