D81.2
BillableSevere combined immunodeficiency [SCID] with low or normal B-cell numbers
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is D81.2 an HCC code?
Yes. D81.2 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 D81.2
For D81.2to 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 D81.2 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
D81.2 is the ICD-10-CM diagnosis code for severe combined immunodeficiency [scid] with low or normal b-cell numbers. A severe inherited immune deficiency where T-cells are absent or very low while B-cells are either low or normal in number. D81.2 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, D81.2 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, D81.2 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.
Differentiate from D81.1 by verifying B-cell count status (low vs. normal). Because D81.2 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 D81.2 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Differentiate from D81.1 by verifying B-cell count status (low vs. normal)
- •Document specific T-cell and B-cell counts from immunological testing
Clinical Significance
Severe combined immunodeficiency with low or normal B-cell numbers represents a SCID phenotype where T-cell development is profoundly impaired while B-cell numbers may be preserved, though B-cell function is still compromised due to lack of T-cell help. This T-negative, B-positive phenotype is commonly associated with interleukin-7 receptor alpha chain deficiency or Janus kinase 3 deficiency.
Documentation Requirements
- ✓Documentation must include flow cytometry showing absent or profoundly reduced T-cells with preserved or low B-cell counts, natural killer cell enumeration, immunoglobulin levels, genetic testing when performed, and treatment including hematopoietic stem cell transplantation or gene therapy.
- ✓Document the specific immunological phenotype (T-B+ or T-B-) to support code assignment.
Commonly Confused Codes
- •D81.1 (severe combined immunodeficiency with low T
- •and B-cell numbers, where B-cells are also severely reduced), D81.4 (Nezelof syndrome with low T-cells and normal B-cells but less severe than SCID), D81.31 (severe combined immunodeficiency due to adenosine deaminase deficiency with a specific enzymatic cause), D81.0 (severe combined immunodeficiency with reticular dysgenesis including myeloid failure).