Modifier 91

Repeat clinical diagnostic laboratory test

Instructions

This modifier is used for laboratory test(s) performed more than once on the same day on the same patient. Tests are paid under the clinical laboratory fee schedule.

Correct Use

  • For necessary tests to obtain subsequent (multiple) test results
  • For tests performed on the same patient on the same day
  • Used with laboratory tests paid under the clinical laboratory fee schedule
  • Clinical Lab Improvement Amendment (CLIA) Waived Test
    • If entity holds valid waiver certificate, append modifier QW

Incorrect Use

  • May not be used when there are standard HCPCS codes available that describe the series of results (e.g., glucose tolerance tests, evocative/suppression testing, etc.)
  • May not be used when tests are rerun to confirm initial results; due to testing problems with specimens and equipment; or for any other reason when a normal, one-time, reportable result is all that is required
  • Does not replace modifiers such as RT, LT, 50, E1-E4, FA, F1-F9, TA, and T1-T9

Claim Example - Laboratory

Pathology example on CMS-1500 claim representing CPT 81000 when repeat service provided on same day. The example shows CPT 81000 billed with no modifier on the first claim line, CPT 81000 with modifier 91 appended on second and subsequent lines.

Resource

 

Last Updated Oct 25 , 2022