Core Risk Adjustment Knowledge
This domain tests whether you understand why a code changes payment before you open a chart. Expect questions on prospective payment, the CMS-HCC model family, hierarchies, model versions, and the difference between a diagnosis that is merely documented and one that is payable.
The model mechanics
Risk adjustment converts diagnoses into predicted cost so that plans caring for sicker members are paid more. Each ICD-10-CM code maps to an HCC - a group of diagnoses with similar expected cost. The risk score, or RAF, equals the demographic factors (age and sex, institutional status, originally-disabled status) plus the sum of disease coefficients, divided by a normalization factor so the average member scores 1.0.
- Prospective use. Dates of service from 1 January to 31 December of the data collection year drive payment for the following payment year; a 2024 encounter is paid in 2025.
- Hierarchies (trumping). Within a condition family only the highest-ranked HCC pays. In CMS-HCC V24, HCC 18 (diabetes with chronic complications) supersedes HCC 19 (diabetes without complications). The trumped condition is still coded when documented; it simply adds nothing to payment.
- Model version must match payment year. V28 removed many codes that paid under V24 and split several condition families, so the same chart can score differently across years.
Worked example
A member has type 2 diabetes with diabetic peripheral neuropathy coded E11.42 at one visit and type 2 diabetes without complications coded E11.9 at another. Only E11.42 is submitted for risk adjustment. It maps to HCC 18; HCC 19 is suppressed by hierarchy even though E11.9 was a valid code for its own encounter. The RAF carries one diabetes HCC. If the same member also has COPD coded J44.9, that maps to a different family (HCC 111) and its coefficient adds on top rather than being trumped.
Traps that cost marks
- Assuming every documented diagnosis raises payment; hierarchy, model exclusions and non-payable codes break that assumption.
- Mixing model years: a code payable in V24 may be deleted or renumbered in V28.
- Confusing RxHCC (Part D drugs) with CMS-HCC (medical).
- Reading a risk score as a clinical severity measure; it predicts cost, not health.
- Forgetting that the demographic portion of the RAF is often the larger share for young or institutionalized members.