The Latest on G Codes

In the United States, current concerns exist that the Center for Medicare and Medicaid Services (CMS) will use “G codes”  to determine changes in policy or payment. A study recently published in the Physical Therapy Journal finds that the G-code functional limitation severity modifier lacks validity for determining functional changes. 

G Codes were mandated by CMS in July 2013 as part of Middle Class Tax Relief and Jobs Creation Act of 2012. Therapists (occupational or physical) choose one of four G code categories: mobility; changing and maintaining body position; carrying, moving, and handling objects; and self care. Therapists select one of out seven functional limitation severity modifier codes. These G Codes reflect the amount of impairment from zero to one hundred percent.

Diane and Alan Jette completed a retrospective observational study of therapists (occupational and physical) at the Cleveland Clinic to assess the validity of G code functional severity limitation modifier codes. Patients completed the AM-PAC, a CMS recommended tool, and were assigned G-codes with severity modifiers based on those scores at initial and follow up visits. The AM-PAC is a post-acute rehabilitation measure which measures three domains: applied cognitive, daily activity, and basic mobility. AM-PAC is validated by the WHO’s International Classification of Functioning, Disability and Health (ICF).

Results demonstrated that sensitivity and specificity were dependent on the initial AM-PAC scores. Those with higher scores were 2.2 to 4.5 times more likely to have improvements in the severity modifier than those with lower scores. Those with lower scores were 2.7 to 4.8 times more likely to have a decline in severity modifier than those with higher scores. As a result, the authors suggest that the use of the G code functional limitation severity modifier should not be utilized for determining functional outcomes as it may not be valid. 

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