R40.2321 ICD-10-CM Code: Coma scale, best motor response, extension, in the field [EMT or ambulance]
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FY 2026 Apr update / Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R99) / Symptoms and signs involving cognition, perception, emotional state and behavior (R40-R46)
R40.2321
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceComa scale, best motor response, extension, in the field [EMT or ambulance]
Coma scale, best motor response, extension, in the field [EMT or ambulance]
CMS-HCC V28
MappedHCC 202
RAF 0.0
CMS-HCC V24
MappedHCC 80
RAF 0.546
ACA/HHS
00
RAF 0
ESRD/PACE
MappedHCC 80
RAF 0.0
RXHCC
00
RAF 0
Code Trumping
Basket needed
Code Book Path
Inclusion Terms
Official- Abnormal extensor posturing to pain or noxious stimuli (< 2 years of age)
- Coma scale motor score of 2
- Extensor posturing to pain or noxious stimuli (2-5 years of age)
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for R40.2321 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for R40.2321 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for R40.2321 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for R40.2321 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for R40.2321 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for R40.2321 in this effective period.
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is R40.2321 an HCC code?
Yes. R40.2321 maps to Coma, Brain Compression/Anoxic Damage under the CMS-HCC V28 risk adjustment model (and Coma, Brain Compression/Anoxic Damage under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for R40.2321
For R40.2321to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed R40.2321 during that encounter, not just copy-forwarded from a problem list.
What This Code Means
R40.2321 is the ICD-10-CM diagnosis code for coma scale, best motor response, extension, in the field [emt or ambulance]. R40.2321 sits in the ICD-10-CM chapter for symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (r00-r99), within the section covering symptoms and signs involving cognition, perception, emotional state and behavior (r40-r46).
Under the CMS-HCC V28 risk adjustment model, R40.2321 maps to Coma, Brain Compression/Anoxic Damage (HCC 202) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, R40.2321 mapped to the same category but with a base RAF weight of 0.546, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Coders should report R40.2321 only when the provider documentation supports the specific condition described, since more specific codes within the same hierarchy can capture additional clinical detail and may carry a higher RAF weight. Because R40.2321 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for R40.2321 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.