B45.1
BillableCerebral cryptococcosis
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is B45.1 an HCC code?
Yes. B45.1 maps to Opportunistic Infections under the CMS-HCC V28 risk adjustment model (and Opportunistic Infections 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 B45.1
For B45.1 to 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 B45.1 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
B45.1 is the ICD-10-CM diagnosis code for cerebral cryptococcosis. A serious fungal infection of the brain caused by Cryptococcus, a fungus found in soil and bird droppings. This condition can cause inflammation of the brain and its protective membranes, leading to symptoms like headache, fever, and confusion. B45.1 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering mycoses (b35-b49).
Under the CMS-HCC V28 risk adjustment model, B45.1 maps to Opportunistic Infections (HCC 6) with a community, non-dual, aged base RAF weight of 0.439. Under the older V24 model, B45.1 mapped to the same category but with a base RAF weight of 0.440 — 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.
Cerebral cryptococcosis is typically associated with immunocompromised patients (HIV/AIDS, organ transplant recipients); verify if an underlying immunodeficiency condition is documented and coded separately. Because B45.1 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 B45.1 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Cerebral cryptococcosis is typically associated with immunocompromised patients (HIV/AIDS, organ transplant recipients); verify if an underlying immunodeficiency condition is documented and coded separately
- •Ensure the documentation specifies 'cerebral' or 'CNS' involvement, as cryptococcosis can affect other sites (pulmonary, disseminated) and requires different codes
Clinical Significance
Cerebral cryptococcosis (cryptococcal meningitis/meningoencephalitis) is one of the most common AIDS-defining infections worldwide and carries significant mortality even with treatment. It is the leading cause of meningitis in sub-Saharan Africa and represents a critical diagnosis requiring emergent antifungal therapy and intracranial pressure management.
Documentation Requirements
- ✓Positive cerebrospinal fluid cryptococcal antigen or India ink preparation
- ✓Cerebrospinal fluid findings: elevated opening pressure, low glucose, elevated protein, lymphocytic pleocytosis
- ✓Neurologic symptoms documented: headache, altered mental status, cranial nerve palsies, neck stiffness
- ✓HIV status and CD4 count documented (typically <100 cells/microL)
- ✓Treatment regimen: induction (amphotericin B + flucytosine), consolidation, maintenance phases
Commonly Confused Codes
- •B45.0 (Pulmonary cryptococcosis) - lung involvement only; if both CNS and lung are affected, code both
- •B45.7 (Disseminated cryptococcosis) - use when multiple organs beyond CNS are involved
- •G03.9 (Meningitis, unspecified) - never use when cryptococcal etiology is confirmed
- •B45.9 (Cryptococcosis, unspecified) - always use B45.1 when cerebral/meningeal involvement is documented