Summary & Overview
CPT 84482: Reverse T3 (rT3) Blood Test
CPT code 84482 represents a laboratory assay measuring reverse T3 (rT3) in blood. Nationally, this code is used in endocrine and metabolic evaluations to assess peripheral thyroid hormone conversion and aid in complex thyroid disorder assessments. The test is performed in clinical and hospital laboratory settings and can inform diagnostic workups for patients with suspected abnormalities in thyroid hormone metabolism.
Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of where and how CPT code 84482 is applied clinically, typical sites of service, and the payer landscape relevant to coverage and billing considerations. The publication also presents benchmarks and coding guidance, outlines common modifiers used with laboratory services, and situates the test within clinical practice for endocrine evaluation.
This summary is intended for a national audience of billing professionals, laboratory managers, and clinicians seeking a clear reference on the clinical role and billing context for CPT code 84482. Data not available in the input is noted where applicable.
Billing Code Overview
CPT code 84482 describes a laboratory test in which a lab analyst measures reverse T3 (rT3) concentration in a patient's blood. This test assesses levels of the inactive thyroid hormone metabolite reverse triiodothyronine, useful in evaluating thyroid hormone metabolism and peripheral conversion of thyroxine.
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Service type: Laboratory test — endocrine/metabolic diagnostic assay
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Typical site of service: Clinical laboratory or hospital laboratory with phlebotomy collection
Clinical & Coding Specifications
Clinical Context
A typical patient is an adult referred by an endocrinologist for measurement of reverse triiodothyronine (reverse T3) to evaluate complex thyroid function when clinical symptoms and standard thyroid tests are discordant. Common scenarios include patients with persistent fatigue, weight changes, or cognitive complaints despite normal serum thyroid-stimulating hormone (TSH) and free thyroxine (free T4) levels; critically ill patients or those with non-thyroidal illness where peripheral conversion of T4 to T3 may be altered; and patients on amiodarone, high-dose corticosteroids, or certain nutritional deficiency states. The clinical workflow: the ordering provider documents the indication and orders CPT 84482 (reverse T3) in the electronic medical record; phlebotomy collects a serum specimen at a typical outpatient laboratory or hospital outpatient draw station; the specimen is labeled and transported to a clinical chemistry or endocrinology laboratory; the lab analyst performs the assay and reports a quantitative reverse T3 result to the ordering clinician through the laboratory information system. Typical site of service is an outpatient laboratory or hospital laboratory; it may also be performed in specialty clinic settings with on-site phlebotomy. Billing uses CPT 84482 for the laboratory analytic service; the professional component modifier 26 may apply when only the reading or interpretation is billed separately by a physician-laboratory director, and the technical component TC may be used when only the instrument and personnel testing are billed by the performing laboratory.