G37.81
BillableMyelin oligodendrocyte glycoprotein antibody disease
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is G37.81 an HCC code?
Yes. G37.81 maps to Multiple Sclerosis under the CMS-HCC V28 risk adjustment model (and Multiple Sclerosis 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 G37.81
For G37.81to 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 G37.81 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
G37.81 is the ICD-10-CM diagnosis code for myelin oligodendrocyte glycoprotein antibody disease. A neurological autoimmune condition where the body produces antibodies against myelin oligodendrocyte glycoprotein, causing inflammation and damage to nerve insulation in the central nervous system. G37.81 sits in the ICD-10-CM chapter for diseases of the nervous system (g00-g99), within the section covering demyelinating diseases of the central nervous system (g35-g37).
Under the CMS-HCC V28 risk adjustment model, G37.81 maps to Multiple Sclerosis (HCC 198) with a community, non-dual, aged base RAF weight of 0.000. Under the older V24 model, G37.81 mapped to the same category but with a base RAF weight of 0.476 — 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.
Requires serological confirmation of MOG antibodies; ensure laboratory results are documented in the medical record. Because G37.81 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 G37.81 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Requires serological confirmation of MOG antibodies; ensure laboratory results are documented in the medical record
- •This is distinct from aquaporin-4 antibody disease (NMO); verify correct antibody type before assigning this code
Clinical Significance
Myelin oligodendrocyte glycoprotein antibody disease (MOGAD) is a recently recognized autoimmune central nervous system demyelinating disorder distinct from both multiple sclerosis and neuromyelitis optica. It has its own specific antibody (anti-MOG), treatment approach, and generally better prognosis than NMO. Accurate coding is critical because treatment pathways differ significantly from other demyelinating diseases.
Documentation Requirements
- ✓Positive MOG-IgG antibody test result documented in the medical record
- ✓Clinical presentation consistent with MOGAD (optic neuritis, transverse myelitis, or ADEM-like presentation)
- ✓Neuroimaging supporting demyelinating disease pattern
- ✓Distinction from NMO (AQP4-antibody negative) and MS documented
- ✓Treatment plan specific to MOGAD (often different from MS treatment)
- ✓Disease course documentation (monophasic vs. relapsing)
Code Also
Commonly Confused Codes
- •G36.0 — Neuromyelitis optica; caused by AQP4 antibodies, not MOG antibodies — distinct disease
- •G35 — Multiple sclerosis; different antibody profile, treatment, and prognosis
- •G36.9 — Acute disseminated demyelination, unspecified; too nonspecific when MOG antibodies are confirmed
- •G37.89 — Other specified demyelinating diseases of CNS; less specific than G37.81
- •G04.81 — Other encephalitis and encephalomyelitis; may overlap clinically but MOGAD has its own code