T86.5
BillableComplications of stem cell transplant
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is T86.5 an HCC code?
Yes. T86.5 maps to Graft-Versus-Host Disease and Stem Cell Transplant Complications under the CMS-HCC V28 risk adjustment model (and Major Organ Transplant or Replacement Status 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 T86.5
For T86.5 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 T86.5 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
T86.5 is the ICD-10-CM diagnosis code for complications of stem cell transplant. Complications that occur after a stem cell transplant, such as rejection, infection, or failure of the transplanted cells to function properly. T86.5 sits in the ICD-10-CM chapter for injury, poisoning and certain other consequences of external causes (s00-t88), within the section covering complications of surgical and medical care, not elsewhere classified (t80-t88).
Under the CMS-HCC V28 risk adjustment model, T86.5 maps to Graft-Versus-Host Disease and Stem Cell Transplant Complications (HCC 454) with a community, non-dual, aged base RAF weight of 0.000. Under the older CMS-HCC V24 model, T86.5 maps to Major Organ Transplant or Replacement Status (HCC 186) with a community, non-dual, aged base RAF weight of 0.910. 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 as the primary code for stem cell transplant complications; additional codes may be needed to specify the type of complication. Because T86.5 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 T86.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Use this code as the primary code for stem cell transplant complications; additional codes may be needed to specify the type of complication
- •Verify documentation clearly indicates stem cell transplant and the specific complication being treated
Clinical Significance
Stem cell transplant complications represent serious post-procedural issues that can affect multiple organ systems and significantly impact patient survival and quality of life. These complications often include graft-versus-host disease, veno-occlusive disease, or infectious complications that require specialized hematology/oncology expertise and intensive monitoring.
Documentation Requirements
- ✓History of stem cell transplant with transplant date and type
- ✓Specific complication type (GVHD, VOD, infection, graft failure)
- ✓Clinical manifestations and affected organ systems
- ✓Laboratory results and diagnostic studies
- ✓Relationship to transplant procedure and conditioning regimen
- ✓Treatment interventions and immunosuppressive therapy
- ✓Response to treatment and disease progression
- ✓Hematology/oncology and transplant team management
Commonly Confused Codes
- •T86.00-T86.09 — Bone marrow transplant complications (different source)
- •D89.81 — Graft-versus-host disease (may be used concurrently)
- •C80.1 — Malignant neoplasm, unspecified (underlying condition)
- •Z94.84 — Stem cell transplant status (routine follow-up)
- •T88.1 — Other complications following immunization