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CPT Modifier 91
Description:
Repeat clinical diagnostic laboratory test
Guidelines/Instructions:
CPT modifier 91 may be submitted to identify an identical laboratory test for the same patient on the same date.
- This modifier may not be submitted when tests are rerun to confirm initial results. This is due to testing problems with specimens or equipment or for any other reason when a normal, one-time reportable result is all that is required.
- This modifier may not be used when other codes describe a series of test results (e.g., glucose tolerance tests)
- For clinical laboratory tests ordered by an ESRD facility, these tests must be submitted with CPT modifier 91 if 1) any single service (same CPT code) is ordered for the same patient, and 2) the specimen is collected more than once in a single day, and the service is medically necessary
- CPT modifier 91 must be submitted with services that meet these criteria, regardless of whether the test is also submitted with HCPCS modifiers CD, CE or EF
- Any line item on a claim that meets these criteria and is submitted with CPT modifier 91 will be included into the calculation of the 50/50 rule
- After calculation of the 50/50 rule, services used to determine the payment amount may not exceed 22
Reference:
- Read more about the 50/50 rule and instructions for submitting CPT modifier 91 in these circumstances in the CMS MLN Matters article MM4101 (PDF, 84 KB)