84439 Assay of free thyroxine
Also known as: free T4, FT4, free thyroxine
Quantitative assay of free thyroxine (free T4) concentration, measuring unbound physiologically active hormone.
In Plain Language
thyroid hormone test
Clinical Context
Gold standard for thyroid function assessment; more specific than total T4; abnormal in hyper/hypothyroidism.
RVU Information
CPT 84439 does not have a physician work RVU assigned by CMS. Reimbursement for this code is determined by payer-specific fee schedules.
Billing & Documentation
Lab and pathology codes require an order from the treating provider with clinical indication. For molecular pathology and genetic testing, document the specific analytes tested and clinical rationale.
How This Code Compares
This code has a work RVU of 0.00, meaning it does not have a physician work component assigned by CMS. In the Pathology & Lab category, 94% of codes share this characteristic.
Specialties
Frequently Asked Questions
What is CPT code 84439?
CPT 84439 (Assay of free thyroxine) is a Pathology & Lab code. Quantitative assay of free thyroxine (free T4) concentration, measuring unbound physiologically active hormone.
Who uses CPT code 84439?
CPT 84439 is used by Clinical Chemistry, Endocrinology, Pathology. Gold standard for thyroid function assessment; more specific than total T4; abnormal in hyper/hypothyroidism.
When is CPT 84439 used?
Gold standard for thyroid function assessment; more specific than total T4; abnormal in hyper/hypothyroidism.
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CPT® is a registered trademark of the American Medical Association. Data sourced from CMS Physician Fee Schedule RVU26A. Descriptions, synonyms, and clinical context are original content by RVU Edge.