The transition from CMS-HCC V24 to V28 has become a major talking point across Medicare Advantage organizations. Many risk adjustment teams spent years building workflows around the logic used in V24. With V28 in place, some of those workflows require adjustment under the updated model.
Certain diagnoses that mapped under V24 may now require more detailed documentation depending on coding specificity and clinical context. Some conditions affect RAF scores differently under V28. Even experienced coding teams are reviewing long-standing processes more closely under the updated model. V28 places greater emphasis on coding accuracy, clinical specificity, and documentation support. As organizations adjust to these changes, some also work with coding and audit partners such as MedCode for additional review and documentation support.
What Changed From V24 to V28?
CMS introduced V28 with updated HCC structures and revised ICD-10 mappings. While the overall purpose of risk adjustment remains the same, the mechanics behind the model have changed in several noticeable ways.
Some diagnosis categories were restructured. Certain ICD-10 codes map differently than they did under V24, and RAF calculations were adjusted through updated coefficient values.
The result is that organizations can no longer assume historical coding behavior will produce the same outcomes under the new version.
Here is a simplified comparison between the two models.
| Area | V24 | V28 |
|---|---|---|
| HCC Structure | Larger number of HCC categories | Updated and consolidated HCC categories |
| ICD-10 Mapping | Broader mapping logic | More selective mapping criteria |
| RAF Calculations | Previous coefficient structure | Rebalanced coefficient values |
| Coding Specificity | Some unspecified diagnoses mapped more broadly | Greater emphasis on detailed diagnosis reporting |
| Diabetes Categories | Broader grouping structure | More refined complication hierarchy |
| Documentation Expectations | Strong documentation required | Increased focus on clinical support and specificity |
| Workflow Impact | Familiar operational workflows | More workflow adjustments needed |
| Compliance Considerations | Existing audit standards | Continued focus on documentation support |
One concern for risk adjustment teams is that conditions with strong RAF impact in V24 may behave very differently under V28. In some cases, the diagnosis still maps, but the overall contribution changes. In others, the diagnosis may no longer map to an HCC category at all.
Key Areas Risk Adjustment Teams Need to Watch
Clinical Specificity Requirements
One of the clearest shifts in V28 is the increased importance of diagnosis specificity.
Under V24, some broader diagnoses still mapped successfully for risk adjustment purposes. V28 applies more specific mapping and documentation requirements in several areas. Coding teams are now relying more heavily on detailed provider documentation to support accurate diagnosis selection.
That often means providers need to document details such as:
- Severity of the condition
- Disease complications
- Chronic versus acute status
- Stage or progression of illness
- Cause-and-effect relationships between diagnoses
In many cases, the issue is clarity rather than note length. For example, documenting a condition without identifying associated complications may affect HCC mapping under V28 even when the patient’s condition remains clinically stable. Because of this, provider education has become a bigger operational focus.
RAF Score Changes
Organizations are also monitoring RAF score movement closely.
A patient population may appear clinically similar from one year to the next, but projected RAF performance can still shift because the model logic has changed.
Several factors contribute to this:
- Revised coefficient values
- Changes to diagnosis hierarchies
- Updated ICD-10 mapping behavior
- Removal or restructuring of certain HCC categories
Importantly, RAF changes should not automatically be viewed as coding problems. In many situations, the score movement reflects structural updates within the CMS-HCC model itself.
ICD-10 Mapping Updates
The ICD-10 mapping revisions in V28 are another major operational consideration.
Some diagnosis codes that mapped to HCCs in V24 now:
- Map differently
- Require greater specificity
- Fall into different categories
- No longer map at all
For coding teams, this means older coding references may need review.
Internal coding references developed during earlier CMS-HCC years may no longer align with current mapping rules. Retrospective review teams are therefore spending more time validating whether commonly used diagnosis codes still behave the same way under the updated model.
Special attention is often given to chronic conditions commonly seen in Medicare Advantage populations, since even small mapping changes can affect RAF performance. Clear communication between departments has become increasingly important during the transition.
Workflow & Compliance Impact
The transition from V24 to V28 affects more than coding alone.
Organizations are reviewing operational workflows tied to:
- Retrospective chart review
- Provider education
- Internal coding audits
- Documentation query processes
- Compliance monitoring
- Quality assurance review
Many teams are also paying closer attention to documentation integrity.
Even when a diagnosis improves RAF performance, it still requires appropriate clinical support. Unsupported diagnoses continue to present compliance risk regardless of model version.
Because of this, organizations are trying to balance coding accuracy with defensible documentation practices.
In practical terms, that means many risk adjustment programs are placing greater emphasis on documentation quality and clinical support.
How Organizations Can Prepare for the V24 to V28 Transition
There is no single approach that works for every organization, but several preparation strategies are becoming common across the industry.
Updating Coding Education Programs
Many coding teams were trained around V24 logic for years, so education updates are often one of the first steps organizations take.
Training efforts commonly focus on:
- Diagnosis categories affected by mapping changes
- Specificity requirements
- Documentation expectations
- Common coding clarification areas
- Updated hierarchy structures
Provider education is especially important because documentation clarity can affect coding accuracy. Smaller sessions tend to be easier for providers to apply in daily workflows.
Reviewing High-Impact Diagnoses
Risk adjustment teams are also identifying diagnoses most likely to affect RAF performance under V28.
This usually includes:
- High-volume chronic conditions
- Diagnoses with revised coefficients
- Conditions with updated specificity requirements
- Frequently used unspecified codes
By reviewing these areas early, organizations can identify where operational adjustments may be needed. In some cases, organizations also use external support from providers such as MedCode for coding reviews and documentation analysis during the transition.
Strengthening Provider Documentation Practices
Clear documentation remains central to successful risk adjustment.
Under V28, providers may need additional support understanding which details are important for diagnosis reporting and coding validation.
Risk adjustment teams are helping by offering:
- Documentation tip sheets
- Specialty-specific examples
- Clarification on common coding gaps
- Feedback from audit findings
The goal is not to encourage unnecessary diagnosis reporting. Instead, the focus is on ensuring the documentation accurately reflects the patient’s condition and complexity of care.
Revising Internal Coding Resources
Many organizations still rely on internal coding guides created around older CMS-HCC model structures.
Those materials may now require revision to reflect:
- Updated HCC categories
- New mapping behavior
- Revised coding examples
- Current documentation expectations
Older resources may need revision to better align with current V28 guidance. Regular review of internal guidance can help reduce confusion across coding teams.
Monitoring RAF Trends Regularly
Organizations are also monitoring RAF trends more frequently.
Regular review can help teams identify:
- Unexpected score variation
- Specialty-specific coding trends
- Documentation gaps
- Audit risk patterns
- Changes in diagnosis capture behavior
The earlier unusual trends are identified, the easier they are to address operationally.
Improving Retrospective Review Workflows
Retrospective review processes remain important under V28, especially when identifying missed diagnoses or documentation gaps.
Review teams are paying closer attention to:
- Clinical validity
- Documentation sufficiency
- Diagnosis specificity
- Mapping accuracy
Some organizations use external coding or audit support during major CMS-HCC transitions.
Organizations such as MedCode may assist with retrospective chart reviews, coding audits, documentation analysis, and provider education support as organizations adapt to updated CMS requirements.
Frequently Asked Questions
- What is the difference between V24 and V28?
V24 and V28 are different versions of the CMS-HCC risk adjustment model used in Medicare Advantage. V28 includes revised HCC structures, updated ICD-10 mappings, adjusted coefficient values, and greater emphasis on diagnosis specificity.
- Why is V28 considered a major update?
The transition affects multiple areas at once, including diagnosis mapping, RAF calculations, documentation expectations, and coding workflows.
- Does V28 lower RAF scores?
RAF impact varies depending on patient populations and diagnosis mix. Some conditions contribute differently under V28 because of updated coefficients and mapping logic.
- How does V28 affect provider documentation?
The newer model places greater emphasis on detailed and clinically supported documentation. Unspecified diagnoses may not behave the same way they did under V24.
- How can organizations prepare for V28?
Common preparation strategies include updating coding education, reviewing high-impact diagnoses, improving documentation practices, revising internal coding resources, monitoring RAF trends, and strengthening retrospective review workflows.
Conclusion
The shift from CMS-HCC V24 to V28 has introduced meaningful changes for Medicare Advantage risk adjustment teams. Updated mapping rules, revised RAF calculations, and increased specificity requirements are leading many organizations to re-evaluate workflows that were built around earlier model logic.
For coding teams, providers, compliance staff, and operational leaders, the transition involves ongoing adjustments to documentation, coding, and workflow processes, along with closer attention to diagnosis accuracy and coding consistency.
As V28 continues to shape risk adjustment operations, maintaining accurate and clinically supported coding practices will remain essential across Medicare Advantage programs.
