CPT code 83518: Immunoassay, single-step, noninfectious analyte2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Reports a single-step immunoassay for an analyte other than an infectious-agent antibody or antigen when a qualitative or semiquantitative result is needed.
Medicare pays $9.64 for 83518 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
$9.64
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
- $9.64
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 83518 covers
83518 identifies a single-step immunoassay for an analyte other than an infectious-agent antibody or antigen. It produces a qualitative or semiquantitative result; reagent-strip testing is an example of this format. Code selection turns on the assay method and result type. A multiple-step immunoassay is represented by 83516, while 83520 represents quantitative immunoassay testing. Radioimmunoassay methodology is identified separately by 83519.
CMS lists a CLIA-waived version of 83518 with modifier QW; sites holding a CLIA certificate of waiver may perform that waived version. Medicare pays the test through the CLFS, not the physician fee schedule. The 2026 national CLFS amount is $9.64 and has remained unchanged since 2020. The same national amount applies in every locality, without geographic adjustment or an office-versus-facility difference.
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 83518
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 83518. 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 83518 with status X (excluded by statute), so the test itself is paid only from the CLFS.
CLIA-waived version (QW)
CMS also lists 83518 with modifier QW, the version labs holding a CLIA certificate of waiver bill. It pays $9.64.
83518 on the lab fee schedule since 2020
83518 · CLFS 2026 Q4 (current)
$9.64
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.
83518 compared with similar tests
- 83516ImmunoassayMultiple-step, qualitative or semiquantitative$11.53
- 83516 identifies a multiple-step immunoassay for an analyte other than an infectious-agent antibody or antigen. Choose 83518 for the single-step qualitative or semiquantitative method.
- 83520Quantitative immunoassayNot otherwise specified$17.27
- 83520 is for quantitative immunoassay testing. 83518 describes a single-step method with a qualitative or semiquantitative result.
- 83519RadioimmunoassayQuantitative measurement$18.40
- 83519 identifies radioimmunoassay methodology. Use 83518 for the single-step immunoassay method, such as a reagent strip.
83518 billing questions
How does 83518 differ from 83516?
83518 describes a single-step qualitative or semiquantitative immunoassay. 83516 identifies a multiple-step method for an analyte other than an infectious-agent antibody or antigen.
When should 83520 be considered?
83520 is for quantitative immunoassay testing. Use 83518 for a single-step qualitative or semiquantitative result.
When is modifier QW relevant?
CMS lists a CLIA-waived version with QW. Sites holding a CLIA certificate of waiver may perform that waived version.
How does Medicare pay for 83518?
Medicare pays it through the CLFS. The national amount applies across localities, without geographic or office-versus-facility adjustment.
Does a reagent strip fit this code?
Yes. Reagent-strip testing is an example of the single-step immunoassay method described by 83518.
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
Fee sheets · Coming soon
Put 83518 and the rest of your codes on one sheet
Your codes at your locality, with payer contracts beside Medicare.
Join the waitlist