Sunday, 22 January 2017

Modifier 90, 91, 99

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 : Acute Hepatitis Panel

CPT 80074 / Modifier 90

Modifier 91

Repeat clinical diagnostic laboratory test


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 – Pathology

Modifier 99

Multiple Modifiers (same line, same code)


When more than four modifiers are needed to describe a service on the same code, replace with modifier 99.

Correct Use
  • Reflect all modifiers involved in Item 19 narrative or electronic equivalent
  • Replace with modifier 99 in Item 24D
  • Documentation must explain all modifiers involved
  • Includes informational and pricing modifiers
  • Certain modifiers may affect payment

Incorrect Use

In this situation, do not append other modifiers in Item 24D

Claim Coding Example

Patient had a Mohs removal (within 90 day global) on the left cheek and then another on the right cheek (RT) by the same provider, repeated twice (i.e., 79, 59, RT) and not enough modifier spaces.

Treatment Description : Mohs micrographic technique, including removal
CPT 17311 /Modifier 99

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