Question: What is the proper way to use modifier GG? Do I append it to a diagnostic mammogram code? Do we need a separate order for the diagnostic exam? Illinois Subscriber Answer: You should report both the screening and diagnostic exams. Append modifier GG (Performance and payment of a screening mammogram and diagnostic mammogram on the same patient, same day) to the diagnostic mammogram code. You will not need an order for the diagnostic exam in this case. Example: 77057 -- Screening mammography, bilateral (2-view film study of each breast) 77055-GG -- Mammography; unilateral. Or if the mammograms are digital, use the following codes: G0202 -- Screening mammography, producing direct digital image, bilateral, all views G0206-GG -- Diagnostic mammography, producing direct digital image, unilateral, all views. Payer preference: Order requirements: Under age 35: No payment allowed for screening mammography. 35-39: Baseline (pay for only one screening mammography performed on a woman between her 35th and 40th birthday). Over age 39: Annual (11 full months have elapsed following the month of last screening). Medicare allows radiologists who interpret a screening mammogram to order and interpret additional mammography films "while a beneficiary is still at the facility for the screening exam" if the screening reveals a potential problem, according to MCPM, chapter 18, section 20.B. And Medicare will pay for both the screening and diagnostic exams.