Q91.2
BillableTrisomy 18, translocation
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is Q91.2 an HCC code?
No. Q91.2 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
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 Q91.2
For Q91.2to 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 Q91.2 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
Q91.2 is the ICD-10-CM diagnosis code for trisomy 18, translocation. Trisomy 18 (Edwards syndrome) caused by a translocation where extra chromosome 18 material is attached to another chromosome; may be inherited from a carrier parent. Q91.2 sits in the ICD-10-CM chapter for congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (q00-qa0), within the section covering chromosomal abnormalities, not elsewhere classified (q90-q99).
Q91.2 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Maps to RxHCC 148 (Mild Intellectual Disabilities) with RAF weight 0.0 in the RxHCC model only. The condition does not impact CMS-HCC models despite the genetic counseling and family screening implications. Coders reviewing Q91.2 should check whether additional documentation would support a more specific child code in the same hierarchy that does map to a payment HCC — capturing the correct specificity is the highest-leverage RAF improvement available within accurate coding.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for Q91.2 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •When translocation is present, investigate parental karyotypes as one parent may be a balanced translocation carrier
- •Document if the translocation is de novo or inherited, as this affects genetic counseling and recurrence risk
Clinical Significance
Trisomy 18 due to translocation may indicate inherited risk and requires genetic counseling for family members. This form can have variable presentation depending on the amount of chromosome 18 material present and may require different management approaches than sporadic cases.
Documentation Requirements
- ✓Karyotype analysis showing translocation involving chromosome 18
- ✓Documentation of unbalanced translocation resulting in trisomy 18
- ✓Parental karyotype studies if indicated
- ✓Family history of chromosomal abnormalities
- ✓Genetic counseling documentation
- ✓Assessment of recurrence risk for family
- ✓Clinical phenotype evaluation
- ✓Breakpoint analysis if available