CPT code 84181: Western blot, interpretation and report2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Western blot analysis measures proteins in blood or another body fluid and includes interpretation and a report.
Medicare pays $17.03 for 84181 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
$17.03
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 84181 covers
Western blot analysis separates proteins in a specimen and uses targeted detection to identify protein bands. Laboratory professionals perform and report the assay on blood or another body fluid. The resulting pattern is interpreted as part of the service; it is not a routine total-protein assay. The code includes the interpretation and report.
Medicare pays 84181 under the CLFS at one national amount per code, with no locality adjustment or office-versus-facility difference. The 2026 national amount is $17.03, unchanged since 2020. The test is paid under the CLFS rather than the physician fee schedule; a separate physician interpretation is also payable under the physician fee schedule with modifier 26.
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 84181
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 84181. 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 84181 with status X (excluded by statute), so the test itself is paid only from the CLFS.
Physician interpretation (modifier 26)
A physician’s interpretation is billed separately with modifier 26 and paid under the physician fee schedule: $17.70 nationally in the office, before locality adjustment.
84181 on the lab fee schedule since 2020
84181 · CLFS 2026 Q4 (current)
$17.03
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.
84181 compared with similar tests
- 84182Western blotImmunological band identification$29.21
- 84181 identifies a Western blot on blood or another body fluid that includes interpretation and a report. Choose 84182 when its code definition matches the service performed.
- 84165Protein electrophoresisSerum fractionation and quantitation$10.74
- 84165 reports serum protein electrophoresis, which evaluates protein fractions. 84181 reports Western blot analysis.
- 84155Total proteinSerum, plasma, or whole blood$3.67
- 84155 is a serum protein assay, not a Western blot. Use 84181 for protein detection by Western blot rather than a serum protein measurement.
84181 billing questions
How does 84181 differ from 84182?
84181 identifies a Western blot on blood or another body fluid that includes interpretation and a report. Choose 84182 when its code definition matches the service performed.
Does 84181 include interpretation?
Yes. The service includes interpretation and a report; a separate physician interpretation is payable under the physician fee schedule with modifier 26.
Can modifier 26 be used for the laboratory test?
Modifier 26 applies to the separately payable physician interpretation, not the laboratory test itself, which is paid under the CLFS.
Is 84181 the right code for a total-protein measurement?
No. 84181 represents Western blot analysis. Code 84155 describes a serum protein assay rather than protein detection by Western blot.
Does Medicare pay different CLFS amounts by locality or setting?
No. Medicare pays one national CLFS amount for 84181 across localities, with no office-versus-facility difference.
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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