Summary & Overview
CPT 82658: Enzymatic Activity Assay Using Radioactive Substrate
CPT code 82658 covers specialized laboratory measurement of intracellular or tissue-derived enzymatic activity using a radioactive substrate. This is a niche clinical laboratory procedure reserved for enzymatic activity tests that are not already described by other specific CPT codes; it enables billing for assays performed with radiolabeled substrates to quantify enzyme function in cellular or tissue specimens. Nationally, accurate coding for such assays supports appropriate laboratory reimbursement, claims adjudication, and clinical documentation for complex diagnostic workflows.
Key payers discussed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. The summary addresses how 82658 is used in practice, typical sites of service (clinical and hospital laboratories), and the clinical contexts in which intracellular or tissue enzyme assays may be ordered.
Readers will learn the clinical purpose and billing intent of 82658, typical service and site settings, and which major payers are relevant for coverage considerations. The publication also outlines expected benchmarks and policy topics readers should expect in the full analysis, such as reimbursement patterns, coding clarification for assays using radiolabeled substrates, and documentation practices needed to support use of this unlisted enzymatic activity procedure. Data not available in the input is noted where applicable.
Billing Code Overview
CPT code 82658 describes an enzymatic activity assay using a radioactive substrate performed by a laboratory analyst to measure intracellular or tissue-derived enzyme activity. This code is intended for use when the procedure is an enzymatic activity test not otherwise listed among other procedures.
Service type: Laboratory — specialized enzymatic assay using radiolabeled substrate
Typical site of service: Clinical laboratory or hospital laboratory environment; specimens may be derived from tissue or cellular samples
Clinical & Coding Specifications
Clinical Context
A typical patient is a 45-year-old referred to the clinical laboratory by a hematology or metabolic specialist for investigation of suspected intracellular enzyme deficiency or for research-level enzymatic assays on tissue or cellular samples. The patient may present with unexplained muscle weakness, hepatosplenomegaly, neurodevelopmental delay, or metabolic crises prompting evaluation for disorders such as lysosomal storage disease, mitochondrial enzyme defects, or other inborn errors of metabolism. A tissue biopsy (e.g., liver, muscle) or isolated cells (e.g., leukocytes, fibroblasts) are collected in the clinic or outpatient surgical suite, transported to a specialized reference laboratory, and processed for cell disruption. The laboratory analyst performs an enzymatic activity assay using a radiolabeled substrate to quantify intracellular enzyme activity not covered by a listed CPT procedure. Results are interpreted by a clinical laboratory professional and reported to the ordering clinician for diagnostic confirmation, treatment planning, or further genetic testing. Typical site of service is an outpatient hospital-based pathology/laboratory or a specialized independent reference laboratory with biosafety capabilities.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
26 | Professional component | When billing only the interpreting professional's portion if the facility bills the technical component separately. |