CPT code 85613: Viper venom test, diluted clotting assay2026 Medicare lab fee · Clinical Laboratory Fee Schedule
A diluted Russell viper venom clotting assay used in coagulation evaluation for lupus anticoagulant, reported when the diluted test is performed.
Medicare pays $9.58 for 85613 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
$9.58
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 85613 covers
85613 identifies the diluted Russell viper venom clotting assay, a test used in coagulation evaluation for lupus anticoagulant, a phospholipid-dependent inhibitor. The assay evaluates clot formation using Russell viper venom and is distinct from the related undiluted Russell viper venom test reported with 85612. It is one component of a laboratory coagulation workup; prothrombin time and partial thromboplastin time are separate tests that may also be reported when performed.
Report 85613 for the diluted assay, rather than 85612 for the related undiluted assay. Medicare pays the test only through the CLFS, at one national amount that applies across localities without an office-versus-facility difference. The 2026 national CLFS amount is $9.58, unchanged from 2020 through 2025. The code is excluded from the physician fee schedule, so payment for the test comes 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 85613
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 85613. 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 85613 with status X (excluded by statute), so the test itself is paid only from the CLFS.
85613 on the lab fee schedule since 2020
85613 · CLFS 2026 Q4 (current)
$9.58
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.
85613 compared with similar tests
- 85612Viper venom timeUndiluted assay$17.49
- Use 85613 for the diluted Russell viper venom assay and 85612 for the related undiluted assay. Select the code that matches the test performed.
- 85730Partial thromboplastin timePTT, plasma or whole blood$6.01
- Code 85730 identifies a partial thromboplastin time, a different coagulation test from the diluted Russell viper venom assay reported with 85613.
- 85610Prothrombin timeRoutine coagulation test$4.29
- Code 85610 identifies prothrombin time, not the diluted Russell viper venom assay reported with 85613.
85613 billing questions
When should 85613 be reported instead of 85612?
Report 85613 for the diluted Russell viper venom assay and 85612 for the related undiluted assay. Select the code that matches the test performed.
How does 85613 differ from a partial thromboplastin time?
85613 identifies the diluted Russell viper venom assay; 85730 identifies a partial thromboplastin time. They are separate coagulation tests.
Can 85613 be reported with other coagulation tests?
Yes, when the other tests are performed as well. Prothrombin time and partial thromboplastin time are separate tests from the diluted Russell viper venom assay.
Does Medicare pay a separate physician interpretation for 85613?
No. Medicare pays 85613 only through the CLFS; the code is excluded from the physician fee schedule.
What should distinguish 85613 in the laboratory record?
The record should identify that the diluted Russell viper venom assay was performed, distinguishing it from the related assay reported with 85612.
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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