G-code Severity Modifiers

Patient scores on select PROMIS® and Neuro-QoL™ measures can be mapped directly to G-code severity modifiers required by the Centers for Medicare and Medicaid.

G-code severity modifier mapping is available for:

  • PROMIS Physical Function
  • PROMIS Upper Extremity Function
  • PROMIS Pain Interference
  • PROMIS Fatigue
  • Neuro-QoL Lower Extremity Function – Mobility
  • Neuro-QoL Upper Extremity Function – Fine Motor, Activities of Daily Living

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Using Self-Report Measures to Select Severity Modifiers


Clinicians who provide physical therapy (PT), occupational therapy (OT), or speech therapy (ST) to improve function report G-codes to the Center for Medicaid and Medicare Services (CMS), as required by CMS Functional Limitation Reporting. For example, a physical therapist may use a code to convey the patient’s current mobility (G8978), the level of mobility the therapy is aiming to achieve (G8979), or the level of mobility at the conclusion of care (G8980). These are known as G-codes for functional reporting.

A G-code severity modifier is used to indicate the level of impairment, limitation, or restriction that the patient is experiencing. This is a percentage ranging from 0% impaired to 100% impaired. G-code modifiers (e.g., CK) are associated with a specific range of impairment (e.g., at least 40% but less than 60% impaired, limited, or restricted). For example, when reporting current mobility, a patient may have 40% to 50% impairment (CK) and treatment aims to reduce that to under 20% impairment (CI).

Assigning a G-code severity modifier (level of impairment) to a patient relies on clinical judgement. A patient self-report measure of function can be used to help a clinician identify the most appropriate modifier to a given individual. As illustrated below, score ranges from select PROMIS® and Neuro-QoL self-report measures have been mapped to each G-code severity modifier. For example, a Neuro-QoL Mobility score between 40.6 and 45.1 is mapped to the G-code modifier CK. 

See Severity Modifier Tables for PROMIS and Neuro-QoL for additional detail