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Clinical Trial Services and Modifiers Q0 and Q1

A clinical trial is defined as an interventional study, meaning that a particular intervention or treatment is being evaluated by qualified researchers who have developed an approved protocol. Interventions include both diagnostic and therapeutic services. Participants are assigned into groups, based on the trial’s protocol. Some groups receive one or more interventions while others may receive none, allowing researchers to determine the effects of the intervention(s) on biomedical or health-related outcomes.

Clinical trials are generally composed of two “arms,” the experimental arm and the control arm. During an experimental arm, participants receive the intervention or treatment that is the focus of the clinical trial. During a control arm, participants receive an intervention or treatment that is already considered to be effective.

CMS has defined rules on which services within a clinical trial are payable by Medicare and also defined Modifiers Q0 and Q1 for use when billing services performed for beneficiaries who are enrolled in clinical trials.

Q0 and Q1 Modifiers Use in Approved Clinical Trials

CMS has defined the Q0 (0=zero) and Q1 modifiers for use on claims filed for Medicare beneficiary services performed during clinical research studies. Appropriate use of these modifiers allows billing providers to indicate the following:

Modifier Q0 

    • The focus of a clinical research study is an investigational item(s) and/or service(s) that is the objective of the investigation. These investigational services may be approved or unapproved by Medicare or may be excluded from a Medicare benefit category or covered by other insurance.
    • When performing an investigational clinical service during an approved clinical research study, the Modifier Q0 is appended to the Category B IDE code in conjunction with the IDE number on the claim.

Modifier Q1

    • Modifier Q1 applies only to routine clinical services performed within the scope of a clinical trial. During the period in which a beneficiary is enrolled in such a trial, he/she may also receive other services that are unrelated to the trial. Examples of these may include routine preventive screening services (e.g., annual mammography) or diagnostic services for a problem unrelated to the purpose or scope of the trial (e.g., ankle X-ray for a traumatic injury, unrelated to the trial). Use of the Modifier Q1 on these unrelated services is inappropriate and may contribute to incorrect payments.
    • During an approved clinical research study, a beneficiary may receive a routine clinical service that is covered by Medicare whether it is performed as part of the study or outside of the clinical study.
    • When such a clinical service is performed within the context of the clinical research study, the Modifier Q1 is added to the service to indicate that the service is being performed as part of clinical management relative to the research study. Such services are not considered investigational and may be performed to prevent, diagnose or treat adverse events related to the research study.
    • When appending a Q1 modifier during the control arm of a research study, the following information is also necessary on the claim:
      • Condition code 30 (non-research services provided to all patients, including managed care enrollees, enrolled in a Qualified Clinical Trial)
      • And either of the following:
        • ICD-9 diagnosis code V70.7 (examination of participant in clinical trial)


        • ICD-10 diagnosis code Z00.6 (examination for participant or control in clinical research program).
    • Modifier Q1 is used for routine clinical services during both the experimental arm and the control arm of the approved trial. The beneficiary’s medical record must include the trial name, sponsor and sponsor-assigned protocol number.
    • If the routine services are associated with a clinical trial involving a Category A or B IDE device, the IDE number is also required on the claim. Charges for a Category A IDE device itself are not covered. Charges for a Category B IDE device may be considered for coverage.

Clinical Service Billing May Include:

    • An investigational item or service that has qualified as a Category B IDE device, and which is reimbursable under the Medicare Part A or Medicare Part B DME benefit.
    • An item or service that is required in order to provide or administer the investigational item or service. Some examples:
      • An administration service for provision of an investigational or noncovered drug
      • Monitoring that is necessary to track a patient’s response to an investigational device or drug
      • Items or services required for the prevention, diagnosis or treatment of research related adverse effects (e.g., lab testing to monitor renal function related to  blood levels of various parameters to measure kidney function)
    • Claims for clinical trial services provided to MA enrollees are processed by the MAC in the jurisdiction in which the provider is located. A provider who intends to provide and bill for such services for MA-enrolled beneficiaries must enroll as a FFS provider with the appropriate MAC in order to submit such claims. MACs will consider these claims within all the applicable FFS rules, with the exception of a waiver of beneficiary liability for any applicable Part A or Part B deductible. Coinsurance amounts on these claims remain as the beneficiary’s responsibility. Clinical trial coding rules for MA claims are the same as those for FFS claims. When both related and unrelated services are provided to a beneficiary on the same day/stay, the institutional provider must split-bill the services. Covered outpatient services, unrelated to the clinical trial, are billed to the MA plan; covered outpatient services related to the clinical trial are submitted to the MAC.

Clinical Service Billing May Not Include:

    • An investigational item or service that is not a qualifying Category B IDE device.
    • Items and services that are not used for direct clinical management of the beneficiary. These would include data collection and analysis performed only for purposes of the study (e.g., bi-monthly PET scans for a beneficiary whose clinical condition would only support a bi-annual PET scan).
    • Items and services that the research sponsors are providing free of charge for beneficiaries who are enrolled in the clinical trial.


    • Paper claim submitters: Submit the IDE number in Item 23 of the CMS-1500 claim form.
    • Electronic claim submitters: Submit the IDE number in Loop 2300 REF02 (REF01=LX).
    • When an IDE number is identified on claims with Modifier Q1, that IDE number is validated by NGS. When the IDE number is identified as invalid, the claim will be returned to the provider with remark code MA130, meaning that the claim is not processable. Such claims must be corrected by the billing provider and resubmitted as new claims.
    • The clinical trial registry number should be preceded by the two alpha characters of "CT" and placed in Field 19 of the paper CMS-1500 claim form or for electronic claims, it should be entered without the "CT" prefix in Loop 2300 REF02 (REF01=P4).

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