# CPT 84479

> Not at a published national rate. CPT 84479 carries status X (statutory exclusion) in the Q3 2021 release. The statutory definition of physician services does not include this item. Treat the blank amount as unpriced, not as $0.

## What it is

An older thyroid lab method that estimates how many binding sites on the blood's carrier proteins are already taken up by thyroid hormone. It does not report a hormone level directly - instead the result is combined with a total T4 measurement to calculate an index that approximates free hormone. Direct free-hormone assays have largely displaced this approach, though the test still appears in some panels and older ordering habits.

## Selected release

- Release: Q3 2021 (2021 C)
- Effective: July 1 – September 30, 2021
- Status indicator: X
- Office (non-facility) national allowed amount: not published
- Facility national allowed amount: not published
- Sequestration: not applied

## RVUs and formula

- Work RVU: not published
- Office (non-facility) practice expense RVU: not published
- Facility practice expense RVU: not published
- Malpractice RVU: not published
- Conversion factor: 34.8931
- Formula: `(work_rvu × work_gpci + pe_rvu × pe_gpci + mp_rvu × mp_gpci) × conversion_factor`

## Source and citation

- Source: Physician relative value file (Q3 2021)
- CMS file: https://www.cms.gov/files/zip/rvu21c-updated-6302021.zip
- Parsed file: PPRRVU21_JUL.csv, row 14,786
- Canonical page: https://localishealth.com/cpt/84479/2014/B
- Release-specific citation URL: https://localishealth.com/cpt/84479/2021/C
- Last significant update: 2026-08-04T03:10:45+00:00