Medical Billing Services

Reimbursement Guidelines for Modifier 90

Reference (Outside) Laboratory: When laboratory procedures are performed by a party other than the treating or reporting physician, the procedure may be identified by adding the modifier 90 to the usual procedure number. For the Medicare program, this modifier is used by independent clinical laboratories when referring tests to a reference laboratory for analysis.

Modifier 90 is used by a physician or clinic when the laboratory tests performed for a patient are performed by an outside or reference laboratory. This modifier is used to indicate that although the physician is reporting the performance of a laboratory test, the actual testing component was a service from a laboratory.

Modifier -90 is used when laboratory procedures are performed by a party other than the treating or reporting physician and the laboratory bills the physician for the service. For example, the physician (in his office) orders a CBC, the physician draws the blood and sends the specimen to an outside laboratory. When outside reference laboratory services are billed using modifier 90:

    • Modifier 90 (reference laboratory) will not bypass clinical edits, subsets, bundling, etc.
    • If some of the blood and/or serum lab procedures are performed by the provider and others are sent to an outside lab and billed with modifier 90, CPT 36415 is not eligible for separate reimbursement.
    • CPT codes 99000 and 99001 (handling fees) are not eligible for separate reimbursement.

Correct Use

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

Inappropriate Use

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

Medical Billers and Coders

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