CPT code 83873: CSF myelin protein, myelin basic protein2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Measures myelin basic protein in cerebrospinal fluid when clinicians assess possible myelin injury or a demyelinating process.
Medicare pays $17.20 for 83873 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
$17.20
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 7 sections
What 83873 covers
This assay measures myelin basic protein, a component of myelin, in cerebrospinal fluid (CSF). Clinicians may request it when assessing possible myelin injury or a demyelinating process. The specimen is CSF, commonly obtained by lumbar puncture. A clinical laboratory performs and reports the measurement. It is distinct from a total CSF protein assay: 83873 targets myelin basic protein rather than the fluid’s overall protein content.
Medicare pays 83873 through the CLFS, with one national amount applying across localities and no office-versus-facility payment difference. The 2026 national CLFS amount is $17.20, unchanged from 2020 through 2025. The test is excluded from the physician fee schedule and is paid only under the CLFS.
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 83873
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 83873. 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 83873 with status X (excluded by statute), so the test itself is paid only from the CLFS.
83873 on the lab fee schedule since 2020
83873 · CLFS 2026 Q4 (current)
$17.20
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.
83873 compared with similar tests
- 83884Neurofilament lightLight chain assay$116.23
- 83873 measures myelin basic protein in CSF; 83884 measures neurofilament light chain, a different protein.
- 83916Oligoclonal bandsCSF and serum comparison$27.39
- 83916 reports oligoclonal band testing, whereas 83873 measures myelin basic protein in CSF.
- 84157Body fluid proteinNon-serum, non-urine sources$4.00
- 84157 measures total protein in a body-fluid specimen; 83873 measures the specific protein myelin basic protein in CSF.
83873 billing questions
When should 83873 be reported instead of a total CSF protein test?
Report 83873 when the laboratory measures myelin basic protein in CSF. Code 84157 measures total protein in a body-fluid specimen.
How does 83873 differ from CSF oligoclonal band testing?
Code 83873 measures myelin basic protein. Code 83916 reports oligoclonal band testing, a different CSF analysis.
Is 83873 paid under the physician fee schedule?
No. Medicare pays this test only under the CLFS, at one national amount across localities with no office-versus-facility payment difference.
How does 83873 differ from neurofilament light chain testing?
Code 83873 measures myelin basic protein in CSF; 83884 measures neurofilament light chain, a different protein.
Does 83873 measure total protein in CSF?
No. It measures the specific protein myelin basic protein, not the overall protein content of the fluid.
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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