When to Report Modifier 91, and When Not To

When to Report Modifier 91, and When Not To

In the course of treating a treatment, it may be necessary to repeat the same laboratory test on the same day to obtain subsequent (multiple) test results. Modifier 91 Repeat clinical diagnostic laboratory test is used to indicate that different levels of service were provided for different specimens. The cytopathologic report must be clear as to why the same test was repeated on the same day.

Modifier 91 is not appropriate when a test is repeated on the same day to:

  • Confirm results
  • Test problems of the specimen
  • Test problems of the equipment
  • Perform multiple tests on the same specimen

In addition to being careful about modifier 91 use, you must be diligent in your code selection. It is inappropriate to append modifier 91 to a procedure and/or HCPCS level II code when another procedure code better describes the test being performed, or when the procedure code describes a series of tests, only one of which is being repeated.

Source: Cahaba GBA, CPT Modifier 91 Fact Sheet, June 16, 2015

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Renee Dustman

Renee Dustman

Renee Dustman is executive editor at AAPC. She has a Bachelor of Science degree in Journalism and a long history of writing just about anything for just about every kind of publication there is or ever has been. She’s also worked in production management for print media, and continues to dabble in graphic design.
Renee Dustman

About Has 423 Posts

Renee Dustman is executive editor at AAPC. She has a Bachelor of Science degree in Journalism and a long history of writing just about anything for just about every kind of publication there is or ever has been. She’s also worked in production management for print media, and continues to dabble in graphic design.

2 Responses to “When to Report Modifier 91, and When Not To”

  1. Kevin Rogers says:

    Your first sentence seems odd “In the course of treating a treatment, it may be necessary to repeat the same laboratory test on the same day to obtain subsequent (multiple) test results.

    Perhaps you mean, “In the course of treating and illness….”

  2. Joyce says:

    When labs are ordered and the same CPT code is used but each test is a distinct test which modifier do use 91, 59 or the new XU. When we bill 87804 for influenza A&B we add modifier 59 now being told it should be 91. I thought if the test was different then that is when the modifier 59 or XU are used. For labs a lot of tests have the same CPT code but are distinct tests. Medicare does not recognize XU when used. Has anyone had issues when billing
    Can someone provide clarification.

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