CPT® code 83516 is used to report a quantitative immunoassay for an analyte that does not have a more specific CPT® code assigned. This test measures the concentration of a particular substance—such as a hormone, protein, or antibody—using immunologic techniques. It is typically performed when testing for a unique or emerging biomarker that cannot be categorized under an existing, designated assay code.
When to Use CPT® Code 83516
Report 83516 when:
- Performing a quantitative immunoassay for a specific analyte not otherwise described by another CPT® code.
- The test involves antigen-antibody reactions to measure the analyte concentration.
- No more specific CPT® code exists for the substance being measured.
- The result is used to aid diagnosis, monitor therapy, or guide clinical decision-making.
Documentation Requirements
To support the use of CPT® 83516, documentation should include:
- The analyte tested and the clinical reason for measurement.
- A description of the assay method used (e.g., ELISA, chemiluminescent immunoassay).
- The clinical purpose and interpretation of results.
- Laboratory report results linked to the ordering provider and patient chart.
Because this is a “not otherwise specified” code, clear documentation ensures proper payer understanding and reimbursement.
Billing Guidelines
- Report 83516 only when a specific immunoassay CPT® code does not exist for the analyte.
- Include a narrative description of the test performed on the claim form.
- May require manual review or prior authorization from payers.
- If part of a larger test panel, follow panel-specific coding rules and avoid duplicate billing.
Example
A provider orders a quantitative immunoassay to measure levels of a novel biomarker involved in metabolic regulation. Because no specific CPT® code exists for this analyte, the laboratory reports the service under CPT® 83516, with documentation describing the assay type, methodology, and purpose.
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