Modifier GG- Screening Mammogram Converted to Diagnostic

Modifier GG is used when both a screening mammogram and diagnostic mammogram are performed on the same patient on the same day.

What is Modifier GG?

Modifier GG is used when a screening mammogram is converted to a diagnostic mammogram on the same date of service.

During a screening mammography examination, an abnormality or other finding may require additional diagnostic imaging before the patient leaves the facility. When Medicare requirements are met, the screening and diagnostic mammography services may both be reported for the same encounter.

Modifier GG is appended to the applicable diagnostic mammography code to communicate that the diagnostic service resulted from findings identified during the screening examination.

The modifier does not indicate that every screening mammogram with an abnormal result qualifies for same-day diagnostic billing. The additional diagnostic service must actually be performed, medically necessary, and supported by the patient's imaging record.

When to Use Modifier GG

Screening Mammogram Is Performed First: The encounter begins with a screening mammography examination.

Additional Diagnostic Imaging Is Needed: Findings from the screening examination indicate that diagnostic mammography is medically necessary.

Diagnostic Mammogram Is Performed the Same Day: The patient receives the additional diagnostic mammography service during the same encounter or date of service.

Both Services Are Properly Reportable: The screening and diagnostic services satisfy applicable Medicare coding and coverage requirements.

Documentation Supports the Conversion: The imaging record should establish the screening service, findings requiring further evaluation, and subsequent diagnostic mammography.

When NOT to Use Modifier GG

Diagnostic Mammogram Only: Do not report GG when the encounter begins as a diagnostic mammography service without a same-day screening mammogram.

Diagnostic Imaging Occurs on Another Date: GG is intended for applicable screening-to-diagnostic mammography performed on the same date.

No Diagnostic Mammography Is Performed: An abnormal screening result alone does not justify GG if no diagnostic mammography service occurs.

Routine Additional Views: Do not automatically append GG simply because additional images are obtained as part of the normal screening service.

Documentation Does Not Support the Conversion: The record should demonstrate why the screening examination required a separate diagnostic mammography service.

Billing Example

A Medicare beneficiary presents for a routine screening mammogram.

During the screening examination, the radiologist identifies an area requiring further evaluation. Additional diagnostic mammography is medically necessary and performed before the patient leaves the facility.

The provider reports the appropriate screening mammography service and the applicable diagnostic mammography service.

Modifier GG is appended to the diagnostic mammography code to indicate that the diagnostic service resulted from the screening examination performed on the same date.

Documentation Requirements

Screening Service: Document that the encounter began as a screening mammography examination.

Screening Findings: Identify the finding or abnormality that required additional diagnostic evaluation.

Diagnostic Service: Document the diagnostic mammography views or examination subsequently performed.

Medical Necessity: The record should establish why additional diagnostic imaging was necessary.

Same Date of Service: Documentation should demonstrate that the screening and diagnostic mammography services occurred on the same date.

Radiology Report: Maintain a complete report describing the imaging performed, relevant findings, interpretation, and recommendations.

Billing and Claim Considerations

Modifier GG provides Medicare with important information when screening mammography leads directly to diagnostic mammography during the same encounter.

The screening service and diagnostic service remain separate services. GG is reported with the diagnostic mammography code rather than used to replace either procedure code.

Providers should ensure that the diagnosis coding appropriately reflects the circumstances of each service. The screening mammogram and subsequent diagnostic evaluation may require different diagnosis reporting based on the patient's findings and applicable coding requirements.

Modifier GG should also not be confused with modifiers identifying the professional or technical components of radiology services. If component billing applies, additional modifiers such as 26 or TC may be necessary according to the service and payer requirements.

Payer rules outside Medicare may differ, so providers should verify whether a commercial insurer or Medicaid program recognizes GG and how it expects same-day screening and diagnostic mammography to be reported.

Common Billing Mistakes

Appending GG to the Screening Code: Modifier GG is used with the applicable diagnostic mammography service when the screening converts to diagnostic mammography.

Using GG for Diagnostic-Only Encounters: The modifier requires an applicable screening mammogram followed by diagnostic mammography on the same date.

Using GG Across Different Dates: A diagnostic examination performed on a later date does not represent the same-day conversion described by GG.

Missing Diagnostic Documentation: The imaging record should explain why the additional diagnostic service was medically necessary.

Confusing GG With Component Modifiers: GG communicates the screening-to-diagnostic circumstance; it does not identify professional or technical components.

Ignoring Payer Requirements: Non-Medicare payers may have different rules for reporting screening and diagnostic mammography services.

Common Denial Reasons

Same-Day Conversion Is Unsupported: Documentation does not establish that screening mammography converted to diagnostic mammography during the same encounter.

Incorrect Modifier Placement: GG is reported with an inappropriate service or claim line.

Medical Necessity Is Unsupported: Documentation does not establish why diagnostic mammography was necessary following the screening examination.

Diagnostic Service Is Not Documented: The record supports the screening mammogram but does not substantiate the separately reported diagnostic service.

Incorrect Diagnosis Reporting: Diagnosis information does not accurately represent the screening and subsequent diagnostic circumstances.

Payer Requirements Are Not Met: The claim fails applicable coverage, coding, or modifier-reporting requirements.

Modifier GG: Screening vs. Diagnostic Mammography

Screening and diagnostic mammography serve different purposes, and Modifier GG helps communicate when both occur during the same encounter.

A screening mammogram is generally performed on an asymptomatic patient for early detection of breast abnormalities.

A diagnostic mammogram evaluates a specific clinical concern, symptom, abnormality, or finding requiring additional investigation.

When an abnormality identified during screening requires immediate diagnostic mammography on the same date, GG communicates the relationship between the two services.

The medical record should clearly establish the transition from screening to diagnostic evaluation rather than simply showing that multiple mammographic images were obtained.

Frequently Asked Questions

Is Modifier GG appended to the screening or diagnostic mammography code?
Modifier GG is appended to the applicable diagnostic mammography code to indicate that the diagnostic service followed a screening mammogram performed on the same date.

Can Modifier GG be used when the patient returns for diagnostic mammography on another day?
No. GG describes applicable circumstances in which screening mammography converts to diagnostic mammography on the same date of service.