CPT code 85635: Reptilase test, fibrin-forming step2026 Medicare lab fee · Clinical Laboratory Fee Schedule
Reptilase testing assesses the final fibrin-forming step in coagulation, helping evaluate prolonged clotting times and distinguish fibrinogen abnormalities from heparin effect.
Medicare pays $9.85 for 85635 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
$9.85
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 85635 covers
The reptilase test measures how quickly fibrinogen in plasma forms a fibrin clot after exposure to reptilase, an enzyme with thrombin-like activity. Clinical laboratories typically perform the assay on citrated plasma as part of an evaluation of abnormal coagulation results, including a prolonged thrombin time. Because heparin does not prolong the reptilase time, comparing it with thrombin time can help distinguish heparin effect from a fibrinogen-related problem.
Report 85635 for reptilase testing, not for thrombin time or prothrombin time. Medicare pays the test only through the CLFS. The 2026 national CLFS amount is $9.85, unchanged since 2020; the same amount applies across localities, without a geographic or office-versus-facility adjustment. The test has no separate physician-fee-schedule payment.
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 85635
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 85635. 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 85635 with status X (excluded by statute), so the test itself is paid only from the CLFS.
85635 on the lab fee schedule since 2020
85635 · CLFS 2026 Q4 (current)
$9.85
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.
85635 compared with similar tests
- 85670Thrombin timeFibrinogen screening$5.77
- Thrombin time assesses clot formation after thrombin is added and can be prolonged by heparin. Reptilase time helps distinguish heparin effect from fibrinogen-related causes.
- 85610Prothrombin timeRoutine coagulation test$4.29
- Prothrombin time evaluates a different portion of the coagulation pathway; it is not a substitute for testing fibrin formation with reptilase.
- 85384Fibrinogen testFunctional activity$9.72
- Fibrinogen activity testing measures fibrinogen function directly, while the reptilase test measures the time to clot formation after reptilase is added.
85635 billing questions
When is reptilase testing useful instead of thrombin time?
Reptilase testing is useful when a prolonged thrombin time needs further evaluation. Comparing the results can help distinguish heparin effect from a fibrinogen abnormality.
Is reptilase testing the same as prothrombin time?
No. Reptilase testing evaluates fibrin formation from fibrinogen, while prothrombin time assesses a different part of the coagulation pathway.
What specimen is used?
The test is generally performed on citrated plasma.
Does heparin affect reptilase time?
Heparin does not prolong reptilase time, unlike thrombin time. Comparing the tests can help identify heparin effect.
How does Medicare pay for this test?
Medicare pays the test through the CLFS, with one national amount across localities and 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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