Types of Medical Codes: ICD-10, CPT, HCPCS and RAF Coding
Medical coding is the foundation of billing, quality reporting, and risk adjustment. This guide explains the main classification systems and how diagnosis codes flow into HCCs and the RAF score.
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ICD-10-CM (Diagnoses)
The International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) codes describe a patient's diagnoses and conditions. With around 70,000 codes, ICD-10-CM is highly specific. These diagnosis codes are the input to risk adjustment: each is mapped, via the ICD-10 to HCC crosswalk, to a Hierarchical Condition Category.
CPT (Procedures)
Current Procedural Terminology (CPT) codes, maintained by the American Medical Association, describe medical, surgical, and diagnostic procedures and services. CPT codes drive professional-service billing and are used in many quality measures.
HCPCS (Products and Services)
The Healthcare Common Procedure Coding System (HCPCS) covers items not in CPT, including durable medical equipment, drugs, supplies, and certain services, especially for Medicare and Medicaid. Level I overlaps with CPT; Level II covers products and non-physician services.
At a glance, the three systems differ in scope — and only one feeds risk adjustment:
| Code system | What it codes | Maintained by | Approx. size | Drives the RAF score? |
|---|---|---|---|---|
| ICD-10-CM | Diagnoses and conditions | NCHS / CMS | ~70,000 codes | Yes — maps to HCCs that build the RAF score |
| CPT | Procedures and services | AMA | ~10,000 codes | No — used for professional billing and some quality measures |
| HCPCS Level II | Products, drugs, supplies, non-physician services | CMS | ~7,000 codes | No — used for Medicare/Medicaid billing |
How Codes Drive the RAF Score
Risk adjustment runs on diagnosis codes. A documented condition is coded in ICD-10-CM, mapped to an HCC, and the HCC contributes its coefficient to the RAF score. Coding specificity has a direct financial impact, and under HCC V28 specificity matters even more.
RAF Coding (Risk-Adjustment Medical Coding)
RAF coding — also called RAF medical coding or risk-adjustment coding — is the specialized practice of reviewing clinical documentation and assigning the ICD-10-CM codes that map to risk-adjusting HCCs. Unlike fee-for-service coding, which centers on the procedures performed at a visit, RAF medical coding focuses on capturing every chronic condition that is monitored, evaluated, assessed, or treated during the calendar year, because each one feeds the patient's HCC and RAF score. See how HCC coding drives the RAF score for the full ICD-10 → HCC → RAF pipeline, and the RAF score cheat sheet for a quick component reference.
Final Verdict
ICD-10-CM, CPT, and HCPCS each serve a distinct purpose, but for risk adjustment the diagnosis codes are decisive. Accurate, specific coding is the bridge between clinical care and correct reimbursement.
Why ICD-10 Specificity Directly Impacts Revenue
The single biggest revenue lever in coding is specificity. The same patient, documented vaguely vs. specifically, produces a different HCC mapping — and therefore a different RAF score and payment. The illustrative example below shows the gap (directional only — confirm exact values with the RAF Score Calculator on the current model).
| How the diabetic patient is coded | Maps to a risk-adjusting HCC? | Illustrative RAF impact |
|---|---|---|
| E11.9 — Type 2 diabetes without complications | Minimal / may not risk-adjust | ~0 (directional) |
| E11.22 + N18.32 — Type 2 diabetes with diabetic CKD, stage 3b | Diabetes-with-complications HCC + CKD HCC (+ interaction) | Materially higher (directional) |
Same patient, same visit — only documentation specificity changed. Multiply that delta across a panel and it is a material revenue difference. Map your real codes with the ICD-10 to HCC crosswalk.
Worked example — from our RAF V24 vs V28 tool
Coding specificity and model version, not the patient, move the revenue. The full worked dollar example (V24 vs V28) is in what a RAF score is.
Source: RAF V24 vs V28 comparison tool. Single illustrative patient; not an average.
From ICD-10 codes to a RAF score in seconds
Paste diagnosis codes; the calculator maps them to HCCs and returns the RAF score.
Open the RAF Score CalculatorFrequently Asked Questions
The three primary systems are ICD-10-CM (diagnoses), CPT (procedures), and HCPCS (products, supplies, and services).
ICD-10-CM diagnosis codes drive risk adjustment: each maps to an HCC that contributes its coefficient to the RAF score.
CPT describes procedures and services; HCPCS Level II covers products, supplies, and services not in CPT, mainly for Medicare and Medicaid.
There are approximately 70,000 ICD-10-CM diagnosis codes, making the system highly specific.
RAF coding (risk-adjustment medical coding) is assigning the ICD-10-CM diagnosis codes that map to risk-adjusting HCCs, capturing every chronic condition documented in the year so the patient's HCC and RAF score is accurate.
This page is educational and does not constitute coding, billing, legal, or clinical advice. Standards, quality measures, and CMS rules change over time; always confirm against current official guidance and your organization's compliance team. CPT® is a registered trademark of the American Medical Association; HEDIS® is a registered trademark of the National Committee for Quality Assurance (NCQA). This page is independent and is not affiliated with, endorsed by, or sponsored by CMS, the AMA, or NCQA.