Summary & Overview
CPT 83921: Single Organic Acid Analyte Measurement
CPT code 83921 identifies a laboratory assay that measures a single organic acid analyte from biological specimens such as serum, plasma, urine, amniotic fluid, or blood spot. This code is used for targeted organic acid testing when clinicians order measurement of one specific metabolite among more than 60 known organic acids. Nationally, single-analyte organic acid testing matters for metabolic diagnostics, toxicology screens, and targeted monitoring in clinical genetics, neonatology, and metabolic disease management.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find an overview of clinical context and service settings, standard billing considerations, and typical sites of service. The publication outlines common use cases for single-analyte organic acid testing, discusses payer coverage patterns at a high level, and highlights operational considerations for ordering and specimen handling. Data not available in the input is noted where applicable.
This summary provides clinicians, laboratory directors, and billing staff with a concise reference to the purpose and application of CPT code 83921, the clinical scenarios in which it is ordered, and the principal payers implicated in coverage decisions for single-analyte organic acid testing.
Billing Code Overview
CPT code 83921 describes a laboratory test in which a single organic acid analyte is measured. The analyte may be any one of more than 60 identified organic acid compounds. The test is performed on a variety of specimen types, including serum, plasma, urine, amniotic fluid, blood spot, or other specimen types, depending on the analyte requested.
-
Service type: Clinical laboratory single-analyte organic acid testing
-
Typical site of service: Clinical laboratory or hospital laboratory; specimens may be collected in outpatient, inpatient, or specialty settings depending on clinical need.
Clinical & Coding Specifications
Clinical Context
A 6-year-old child presents to a pediatric metabolic clinic with a history of delayed development, failure to thrive, recurrent vomiting, and episodic lethargy. The clinician suspects an inborn error of metabolism or an acquired metabolic disturbance and orders targeted organic acid testing to evaluate specific metabolites in urine. A urine specimen is collected in the outpatient clinic and sent to the clinical chemistry laboratory. The lab analyst performs 83921 to measure a single organic acid analyte (for example, methylmalonic acid or lactic acid) using gas chromatography–mass spectrometry or liquid chromatography–tandem mass spectrometry. Results are returned to the ordering provider and documented in the electronic medical record; abnormal findings prompt genetics referral, nutritional management, or hospital admission for metabolic stabilization.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | Use when billing professional interpretation separate from technical component provided by a reference lab. |
TC | Technical component | Use when billing only the laboratory technical processing and instrumentation portion. |
59 | Distinct procedural service | Use when the organic acid test is distinct and separate from another performed procedure on the same day. |
91 | Repeat clinical diagnostic lab test | Use when the same test is repeated on a subsequent specimen to monitor therapy or verify results. |
90 | Reference laboratory | Use when the service is performed by a qualified outside reference laboratory. |
52 | Reduced services | Use when the test is partially performed or limited in scope. |
53 | Discontinued procedure | Use when specimen collection or analysis was started but discontinued for documented clinical reasons. |
22 | Increased procedural services | Use when work or complexity substantially exceeds typical requirements for the test (rare for routine lab tests; document justification). |
59 | Distinct procedural service | Use when a distinct analyte measurement is billed separately from bundled testing (ensure correct use per payer policy). |
90 | Reference laboratory | Use when the performing lab is different from the billing lab and report originates from an outside reference lab. |
91 | Repeat clinical diagnostic laboratory test | Use for repeat testing on a separate specimen due to quality control, therapy monitoring, or verification. |
QW | CLIA waived test | Use when the laboratory test is CLIA-waived (rare for 83921). |
AS | Physician assistant, nurse practitioner, clinical nurse specialist services performed in part | Use when applicable to provider billing rules for professional interpretation. |
| Taxonomy Code | Specialty | Notes |
|---|---|---|
207Q00000X | Clinical Laboratory Geneticist | Interprets metabolic and organic acid testing results; consults on rare inherited metabolic disorders. |
2080P0005X | Pathology - Clinical Pathology | Laboratory oversight, test validation, quality control and reporting. |
207R00000X | Biochemical Geneticist | Specialist in inherited metabolic disorders and interpretation of organic acid profiles. |
2083P0200X | Pediatric Laboratory Medicine | Pediatric-focused laboratory testing and specimen handling. |
363L00000X | Genetic Counselor | Provides counseling based on test results and coordinates further genetic testing. |
Related Diagnoses
| ICD-10 Code | Description | Clinical Relevance |
|---|---|---|
E71.1 | Organic acid metabolism disorders | Directly indicates inherited organic acidurias evaluated by 83921. |
E88.8 | Other metabolic disorders | Used for metabolic abnormalities where a targeted organic acid assay assists diagnosis. |
R63.3 | Feeding difficulties and mismanagement | Common in children with metabolic disorders prompting metabolic testing. |
R62.0 | Delayed milestone in childhood | Developmental delay can be a presenting feature leading to organic acid testing. |
E70.0 | Phenylketonuria (classical) | Part of differential metabolic evaluations; organic acid testing may assist in broader metabolic panels. |
Related CPT Codes
| CPT Code | Description | Relationship to This Procedure |
|---|---|---|
80055 | Basic metabolic panel | Often ordered concurrently to assess electrolytes and renal function that affect organic acid interpretation. |
84152 | Lactic acid; blood | Lactic acid measurement may be ordered instead of or in addition to a single organic acid analyte in suspected lactic acidosis. |
82043 | Phenylalanine; quantitative | Amino acid metabolism testing commonly performed alongside organic acid analysis in metabolic workups. |
83898 | Mass spectrometry, qualitative or quantitative, multiple compounds | Performed in the lab workflow for organic acid analysis using MS-based methods; may be billed for multiplex testing. |
82728 | Carnitine, total and free | Carnitine testing is frequently used with organic acid profiles when fatty acid oxidation disorders are suspected. |