Medicare Part B modifiers – 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.

Medicare Part B modifiers – 91


Repeat clinical diagnostic laboratory test: In the same course of treatment of the patient, it may be necessary to repeat the same laboratory test on the same day to obtain subsequent (multiple) test results. Under these circumstances, the laboratory test performed can be identified by its usual procedure number and the addition of the modifier 91.

Note: This modifier may not be used when tests are rerun to confirm initial results; due to testing problems with specimens or equipment; or for any other reason when a normal, one-time, reportable result is all that is required.

This modifier may not be used when other code(s) describe a series of test results (e.g., glucose tolerance tests, evocative/suppression testing). This modifier may only be used for laboratory test(s) performed more than once on the same day on the same patient

Instructions for Modifier 90

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






Modifier 91 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

Reimbursement Guidelines

Moda Health requests claims for laboratory tests and services to be submitted by the laboratory performing the services.

Moda Health strongly discourages providers from submitting claims for lab tests sent to an outside reference laboratory by using modifier 90.

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.

To define when the Plan recognizes services appended with Modifier 90.

Scope Applies only to Alaska lines of business, products and providers

Policy Laboratory services must be submitted directly to the Plan by the provider who actually performed the laboratory test. Reimbursement will be made directly to the laboratory that performed the service(s), for those laboratory services covered by the member’s benefits.

Providers who bill for laboratory services that are performed by an outside laboratory or by a party other than the treating or reporting physician or other qualified healthcare professional must be submitted with Modifier 90.

Use of modifier 90 indicates that a laboratory test was performed by a party other than the treating or reporting physician or other qualified health care professional. The Plan will no longer reimburse for laboratory tests billed by a party other than the performing laboratory nor tests submitted with modifier 90 appended to the laboratory test procedure code.

Medicare Policy

Policy: Although Medicare payment may generally be made to an independent clinical laboratory only for those tests that it performs, payment may also be made to a laboratory for a test that is on the clinical laboratory fee schedule that it has referred to another laboratory, provided the referring laboratory meets one of the following three conditions:

– It is located in, or is part of, a rural hospital;

– It is wholly-owned by the reference laboratory; or both it and the reference laboratory are wholly-owned subsidiaries of the same entity; or – It refers no more than thirty (30) percent of the clinical laboratory tests annually to other laboratories, (not including referrals made under the wholly-owned proviso, above).

The Medicare allowed amount for a referred test is based on the fee schedule in effect where the test was performed. For services that are carrier priced, the reimbursement amount will be based upon the price developed by the carrier processing the claim.

The billing laboratory, whether it is the referring laboratory or the reference laboratory, must submit its claim to the carrier in which it is enrolled by reason of having a physical presence.

When the billing laboratory is the referring laboratory it must:

– Identify the referred service as such by use of modifier 90, and

– Identify the reference laboratory by specifying its CLIA number and address (i.e., the address where the test was actually performed).

The clinical diagnostic laboratory will not have to submit separate claims for referred and performed services. The CLIA numbers from both the billing and reference laboratories must be submitted on the same claim. The presence of the ‘90’ modifier at the line item service identifies the referral tests. Referral laboratory claims are only permitted for independently billing clinical laboratories, specialty code 69.

The billing laboratory submits, on the same claim, tests referred to another (referral/rendered) laboratory, with modifier 90 reported on the line item and reports the referral laboratory’s CLIA number in: X12N 837 (HIPAA version) loop 2400, REF02. REF01 = F4 EXAMPLE: A physician has ordered the DEF independent laboratory to perform glucose testing and tissue typing for a patient. Since the DEF Laboratory is approved to perform only at the routine chemistry LC level (which includes glucose testing), it refers the tissue-typing test to the GHI laboratory.

National Standard Format (NSF) Electronic Claims:

Suppliers that submit claims in the NSF format may not combine services that they performed themselves and any that they referred to another laboratory on the same NSF claim form. If a billing laboratory performs some testing and refers the remaining tests to another (reference) laboratory to perform, the laboratory must segment the services and submit two separate claims. If services are referred to more than one laboratory, a separate claim must be submitted for each reference laboratory to which services were referred. Referral laboratory claims submitted to carriers are permitted only for independent clinical laboratories, specialty code 69. The line items submitted for referred lab test must contain a modifier 90. CLIA number:

An NSF claim for laboratory testing will require the presence of the performing laboratory’s CLIA number: if tests are referred to another laboratory, the CLIA number of the laboratory where the testing is rendered is submitted on the claim. An NSF electronic claim for laboratory testing must be submitted using the following format:

The electronic claim will require two submittals when billing for performed services and reference services. For the first submittal the CLIA number for the billing lab must be item 23 of the claim with the tests they performed. For the second claim, the CLIA number for the reference laboratory must be in item 23 of the claim where the tests were not performed by the billing lab. The presence of the ‘90’ modifier at the line item identifies the referral tests. Referral laboratory claims are only permitted for independently billing clinical laboratories, specialty code 69.

Paper Claim Submission To Carriers

An independent clinical laboratory that elects to file a paper claim form shall file Form CMS-1500 for a referred laboratory service (as it would any laboratory service). The line item services must be submitted with a modifier 90. An independent clinical laboratory that submits claims in paper format) may not combine non-referred (i.e., self-performed) and referred services on the same CMS 1500 claim form. When the referring laboratory bills for both non-referred and referred tests, it shall submit two separate claims, one claim for non-referred tests, the other for referred tests. If billing for services that have been referred to more than one laboratory, the referring laboratory shall submit a separate claim for each laboratory to which services were referred. (unless one or more of the reference laboratories are separately billing Medicare). A paper claim that contains both non-referred and referred tests is returned as unprocessable.

When the referring laboratory is the billing laboratory, the reference laboratory’s name and address shall be reported in item 32 on the CMS-1500 claim form to show where the service (test) was actually performed Also, the CLIA number of the reference laboratory shall be reported in item 23 on the CMS-1500 claim form. A paper claim that does not have the name and address of the reference laboratory in item 32 or the CLIA number of the reference laboratory in item 23 is returned as unprocessable. EXAMPLE: A physician has ordered the ABC Laboratory to perform carcinoembryonic antigen (CEA) and hemoglobin testing for a patient.

Since the ABC Laboratory is approved to perform tests only within the hematology LC level (which includes the hemoglobin test), it refers the CEA testing (which is a routine chemistry LC) to the XYZ laboratory.

Result: The ABC laboratory submits a claim for the hemoglobin test and reports its CLIA number in item 23 on the CMS-1500 form. Since the ABC laboratory referred the CEA test to the XYZ laboratory to perform, the ABC laboratory (billing laboratory) submits a second claim for the CEA testing, reporting XYZ’s CLIA number in item 23 on the CMS-1500 form. The XYZ laboratory’s name, and address is also reported in item 32 on Form CMS-1500 to show where the service (test) was actually rendered.