Clinical Diagnostic Laboratory Services – GY Modifier

Effective January 1, 2004, laboratories should add the GY modifier to the CPT procedure codes for any service where the appropriate diagnosis for that service is on the list of diagnoses that are not covered by Medicare.

In November 2002, Medicare implemented 23 national coverage determinations (NCDs) for clinical diagnostic laboratory services. These NCDs are specific down to the ICD-9-CM code level and included lists of ICD-9-CM codes that are covered and those that are not covered by Medicare. The ICD-9-CM codes that are not covered by Medicare are codes that are excluded from coverage based on technical denials, such as routine screening services, rather than denial due to lack of medical necessity. Laboratories are permitted to bill beneficiaries for services that are not covered by Medicare for reasons other than medical necessity without providing for an Advance Beneficiary Notice (ABN).

Effective January 1, 2004, the clinical diagnostic laboratory service edit module will consider the presence of the GY modifier in selecting the appropriate response for claims for clinical diagnostic laboratory services. Use of the GY modifier will result in a not covered response from the edit module in all cases.