CPT code 83520: Quantitative immunoassay, not otherwise specified2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Reports quantitative immunoassay measurement of an analyte other than an infectious-agent antigen or antibody when no more specific code identifies the assay.
Medicare pays $17.27 for 83520 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
$17.27
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
- QW · CLIA-waived test
- $17.27
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 83520 covers
This code reports quantitative measurement of a substance by immunoassay when the analyte is not an infectious-agent antigen or antibody and no more specific code describes the assay. It is a method-and-measurement category rather than a named analyte test. Clinical laboratories and office laboratories report it for quantitative immunoassay testing ordered by a treating clinician.
Select the code based on the quantitative immunoassay performed, not merely because a test uses an immunoassay method; use a more specific code when it describes the analyte or method. CMS lists a CLIA-waived version with modifier QW for sites holding a CLIA certificate of waiver. Medicare pays this test through the CLFS at one national amount per code across states and localities, with no geographic adjustment or office/facility difference. The 2026 national CLFS amount is $17.27, unchanged from 2020 through 2026. The test is paid only from 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 83520
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 83520. 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 83520 with status X (excluded by statute), so the test itself is paid only from the CLFS.
CLIA-waived version (QW)
CMS also lists 83520 with modifier QW, the version labs holding a CLIA certificate of waiver bill. It pays $17.27.
83520 on the lab fee schedule since 2020
83520 · CLFS 2026 Q4 (current)
$17.27
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.
83520 compared with similar tests
- 83516ImmunoassayMultiple-step, qualitative or semiquantitative$11.53
- Code 83516 is for a non-antibody immunoassay. Code 83520 identifies quantitative immunoassay testing not otherwise specified.
- 83518ImmunoassaySingle-step, noninfectious analyte$9.64
- Code 83518 identifies an immunoassay performed by a dipstick method. Code 83520 describes quantitative immunoassay testing not otherwise specified.
- 83519RadioimmunoassayQuantitative measurement$18.40
- Code 83519 identifies a non-antibody radioimmunoassay. Code 83520 does not specify radioimmunoassay.
- 83521Free light chainsEach light-chain type$17.27
- Code 83521 identifies testing for free immunoglobulin light chains. Use 83520 for quantitative immunoassay testing not otherwise specified.
83520 billing questions
When should this code be used instead of 83516?
Code 83520 describes quantitative immunoassay testing not otherwise specified. Code 83516 is for a non-antibody immunoassay; select the code that describes the service performed.
Can modifier QW be reported?
CMS lists a CLIA-waived version with QW for testing performed by a site holding a CLIA certificate of waiver.
Is this code paid under the physician fee schedule?
No. Medicare pays the test through the CLFS, with one national amount across localities and no office/facility payment difference.
Should this code be used when a specific analyte code exists?
Use the more specific code when it describes the analyte or assay performed. Code 83520 is for quantitative immunoassay testing not otherwise specified.
How does 83520 differ from 83519?
Code 83519 identifies a non-antibody radioimmunoassay. Code 83520 describes quantitative immunoassay testing without specifying radioimmunoassay.
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
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