D81.89
BillableOther combined immunodeficiencies
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is D81.89 an HCC code?
Yes. D81.89 maps to Severe Combined Immunodeficiency and Other Immune Disorders under the CMS-HCC V28 risk adjustment model (and Disorders of Immunity 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 D81.89
For D81.89to 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 D81.89 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
D81.89 is the ICD-10-CM diagnosis code for other combined immunodeficiencies. A rare condition where the immune system is weakened due to multiple genetic defects, but the specific defects do not fit into other defined categories. D81.89 sits in the ICD-10-CM chapter for diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism (d50-d89), within the section covering certain disorders involving the immune mechanism (d80-d89).
Under the CMS-HCC V28 risk adjustment model, D81.89 maps to Severe Combined Immunodeficiency and Other Immune Disorders (HCC 114) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, D81.89 maps to Disorders of Immunity (HCC 47) with a community, non-dual, aged base RAF weight of 0.472. 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.
Use this code for combined immunodeficiencies that are not otherwise specified in categories D81.0-D81.7. Because D81.89 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 D81.89 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
Clinical Significance
Other combined immunodeficiencies encompasses a heterogeneous group of primary immunodeficiency disorders affecting both cellular and humoral immunity that do not fit into the specifically defined SCID or other D81 subcategories. These conditions include ZAP-70 deficiency, interleukin-2 receptor deficiency, DOCK8 deficiency, and other rare genetic immunodeficiencies with combined T-cell and B-cell dysfunction.
Documentation Requirements
- ✓Documentation must specify the particular combined immunodeficiency diagnosed, including genetic testing results when available, lymphocyte subset analysis, immunoglobulin levels, functional immune testing, and clinical manifestations.
- ✓Explain why the condition does not fit other D81.0-D81.82 subcategories.
- ✓Document the specific infections and complications managed.
Commonly Confused Codes
- •D81.0 through D81.82 (specific combined immunodeficiency subtypes that should be used when applicable), D81.9 (combined immunodeficiency, unspecified, when no specific type is identified), D83.8 (other common variable immunodeficiency for primarily antibody-mediated defects), D84.89 (other immunodeficiencies for non-combined defects).