Modifier 90

Reference (Outside) Laboratory


Sometimes a clinical diagnostic independent lab, place of service (POS) 81, refers a specimen to another lab for testing, where a modifier 90 is appended.

Correct Use

  • Outside laboratory performs procedure, unrelated to treating/reporting physician
    • In most cases, lab furnishing the service would bill the claim
  • Possible for one lab to bill service performed by another lab
    • Referring = referring specimen to another laboratory for testing
    • Reference = lab that receives specimen from another lab and performs one or more tests on such specimen
  • Must append modifier 90 to referred laboratory test code
    • Item 20 mark "Yes" = outside lab
    • Purchase price must be reflected under charges
    • Complete item 32 with NPI, name and address where performed
  • Appropriate modifier 90 claims include two different Clinical Lab Improvement Amendment (CLIA) numbers
    • Reflect billing provider information
    • Laboratory where services were performed (reference lab)
  • Bill claims with modifier 90 and without modifier 90 separately
  • If no purchased services, leave item 20 blank

Inappropriate Use

  • Do not report modifier 90 with anatomic pathology and lab services
  • Do not append modifier 90 for drawing fee (36415)
    • Cannot be referenced out to another lab

Claim Coding Example

Treatment Description CPT/Modifier
Acute Hepatitis Panel 80074 90




Last Updated Dec 09 , 2023