CPT code 84442: TBG assay, protein level2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Measures thyroxine-binding globulin to investigate altered thyroid hormone binding when total thyroid hormone results conflict with the clinical picture.
Medicare pays $14.78 for 84442 under the 2026 Clinical Laboratory Fee Schedule: one national amount, the same in every state and setting.
Medicare lab fee · CLFS 2026 Q4
National CLFS amount
$14.78
In effect since Jan 1, 2026. The same amount in every state, payment locality and setting.
- Geographic adjustment
- None
- Office vs facility
- Same
- Since 2020
- Unchanged
- CMS updates
- Quarterly
Medicare pays the lesser of the lab’s charge and this amount. Patients usually owe no Part B deductible or coinsurance for covered clinical lab tests.
On this page 8 sections
What 84442 covers
This assay measures thyroxine-binding globulin (TBG), a circulating protein that carries thyroid hormones. Clinicians may order it when total thyroid hormone results do not fit the patient’s symptoms or other thyroid tests, or when a change in binding proteins is suspected. Pregnancy and estrogen exposure can raise TBG, while nephrotic syndrome can lower it. Primary care clinicians and endocrinologists commonly order the test through outpatient laboratories.
Report 84442 when TBG itself is measured; total or free thyroxine tests measure different analytes. Medicare pays the test under the CLFS at one national amount across states and localities, with no office-versus-facility payment difference. The 2026 national CLFS amount is $14.78, unchanged since 2020. The test is paid only through the CLFS, not the physician fee schedule.
This summary was written with AI assistance from CMS Clinical Laboratory Fee Schedule data. Amounts on this page come directly from CMS files.
How Medicare pays 84442
Clinical lab tests aren’t priced like physician services. They’re paid from their own fee schedule, with its own rules. See the whole lab fee schedule.
One national amount
CMS sets a single Clinical Laboratory Fee Schedule amount for 84442. There’s no geographic (GPCI) adjustment, so it pays the same in every state and payment locality.
No office or facility rate
Lab tests aren’t built from relative value units, so there’s no office and facility split: the place of service doesn’t change the CLFS amount.
Updated every quarter
CMS republishes the CLFS each quarter. New tests, often proprietary laboratory analyses (PLA codes), join during the year; existing amounts are updated each January.
Excluded from the physician fee schedule
The physician fee schedule lists 84442 with status X (excluded by statute), so the test itself is paid only from the CLFS.
84442 on the lab fee schedule since 2020
84442 · CLFS 2026 Q4 (current)
$14.78
Unchanged since Jan 1, 2020
27 quarterly CLFS releases on file, first CLFS 2020 Q1. A code missing from a quarter wasn’t on that release.
84442 compared with similar tests
- 84436Total T4Total thyroxine$6.87
- This code measures total thyroxine, including hormone bound to proteins. Code 84442 measures the TBG carrier protein.
- 84439Free T4Unbound thyroxine$9.02
- This code measures free thyroxine, the unbound hormone fraction. Code 84442 measures TBG, not thyroid hormone.
- 84443TSH testThyroid-stimulating hormone$16.80
- This code measures thyroid-stimulating hormone, a pituitary hormone. Code 84442 measures a thyroid hormone-binding protein.
84442 billing questions
When is a TBG assay useful instead of a total T4 test?
TBG measures the hormone-binding protein itself. Total T4 measures bound and unbound thyroxine, so a TBG result can help explain a total T4 result affected by altered binding proteins.
How does this differ from a free T4 test?
A TBG assay measures the carrier protein, while free T4 measures unbound thyroxine. The tests answer different questions and are not interchangeable.
What should the medical record support?
Documentation should identify the thyroid-related clinical concern and why measuring TBG is relevant, such as a suspected binding-protein change or discordance between total thyroid hormone results and the clinical picture.
How does Medicare pay for this test?
Medicare pays the assay through the CLFS at one national amount, without a locality or office-versus-facility adjustment. It is paid only through the CLFS.
Is TBG the same test as thyroid-stimulating hormone?
No. TBG measures a thyroid hormone carrier protein; thyroid-stimulating hormone measures a pituitary hormone used to assess thyroid regulation.
Where this amount comes from
FeeBase reads lab amounts directly from the CMS Clinical Laboratory Fee Schedule file for the quarter: one row per code, with its payment indicator and national amount. Contractor-priced tests are labeled, never given a made-up amount. Amounts are Medicare payment limits, not a patient’s bill or a commercial rate.
CMS CLFS 2026 Q4 · effective Oct 1, 2026 through the day before Jan 1, 2027
Show the CMS file line behind this amount
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