DRG, APC, Fee Schedule, RBRVS, and Risk Adjustment

Common Reimbursement Methodologies

Reimbursement methodologies are the payment systems that translate claim data into dollars. CCA questions rarely require contract math, but they consistently require you to recognize the payment system involved and the coded data that feed it. Setting drives the methodology: inpatient facility, outpatient facility, and professional services each use different payment logic.

DRG Concepts (Inpatient Facility)

Diagnosis-related groups (DRGs), tested most often as Medicare Severity DRGs (MS-DRGs), classify acute inpatient stays under the Inpatient Prospective Payment System. The DRG assignment is driven by the principal diagnosis (the condition established after study to be chiefly responsible for the admission), secondary diagnoses that qualify as a complication or comorbidity (CC) or major complication or comorbidity (MCC), major procedures, discharge status, sex, and age. A single MCC can move a stay into a higher-weighted three-tier DRG and materially change payment.

A DRG question may show that one secondary diagnosis changes the payment group. That fact alone does not make the code right or wrong. The code must meet reporting rules, be clinically supported, and be documented by the provider. DRG impact should prompt careful validation, never upcoding (assigning a higher-paying code that the record does not support).

APC Concepts (Outpatient Facility)

Ambulatory Payment Classifications (APCs) drive hospital outpatient facility payment under the Outpatient Prospective Payment System. CPT and HCPCS codes, status indicators, packaging, modifiers, and medical-necessity rules all affect outpatient facility payment. Under packaging, certain ancillary or integral services (for example, minor supplies, observation, or some drugs) are bundled into the payment for a primary service rather than paid separately. Improperly unbundling packaged services to gain extra payment is a compliance violation.

Physician Fee Schedule and RBRVS (Professional)

Professional claims use CPT, HCPCS Level II, ICD-10-CM diagnoses, and modifiers. The Medicare Physician Fee Schedule (MPFS) is built on the Resource-Based Relative Value Scale (RBRVS). Each service has three relative value units (RVUs) — physician work, practice expense, and malpractice — each adjusted by a Geographic Practice Cost Index (GPCI), summed, and multiplied by a national conversion factor (a dollar figure CMS sets annually). The formula in concept: payment = [(work RVU x GPCI) + (PE RVU x GPCI) + (MP RVU x GPCI)] x conversion factor.

HCC and Risk Adjustment

Hierarchical Condition Categories (HCCs) support risk adjustment for Medicare Advantage and similar plans, using diagnosis data to estimate patient complexity and expected cost as a risk adjustment factor (RAF) score. HCC capture requires specific, current documentation. Chronic conditions must show MEAT — Monitored, Evaluated, Assessed, or Treated — during the encounter. Diagnoses do not carry forward automatically year to year; each must be re-documented annually.

Quick Comparison

How a Coding Change Moves Payment

The exam loves scenarios where one coded data element shifts the payment, then asks whether that justifies the change. The answer is always: only if the record supports it.

Worked DRG Example

A patient is admitted for pneumonia (the principal diagnosis). The chart also documents acute respiratory failure that was treated with BiPAP. Acute respiratory failure is an MCC. If the coder captures it as a supported secondary diagnosis, the case groups to a higher-severity, higher-weighted DRG. That is correct capture, not upcoding, because the documentation and treatment support it. Contrast this with adding acute respiratory failure when the record shows only mild dyspnea and no respiratory-failure treatment — that would be upcoding and a compliance violation.

The data element is identical; the documentation is what separates compliant from fraudulent.

Other Payment Systems to Recognize

Beyond the big four, the CCA may name additional prospective payment systems by setting. Match them quickly:

Capitation and Value-Based Payment

Capitation pays a fixed per-member-per-month amount regardless of services used, shifting financial risk to the provider. Fee-for-service pays per service rendered. Risk-adjustment HCC coding matters most under capitated and Medicare Advantage arrangements because the RAF score, not the volume of services, drives revenue. The exam tests recognition of these models, not their math: know that capitation is prepaid and population-based, while DRG, APC, and the fee schedule are tied to the specific encounter and its coded data.

POA Indicators and Sequencing Traps

Inpatient DRG accuracy also depends on the present on admission (POA) indicator, which flags whether each diagnosis existed at admission (Y), developed during the stay (N), was clinically undetermined (W), or is exempt (1/U). POA reporting affects whether a condition counts toward the DRG and whether it is treated as a hospital-acquired condition (HAC), which Medicare may exclude from raising payment. A common trap presents a complication that arose after admission and asks whether it should drive a higher-weighted DRG — the POA = N status often blocks that increase.

Sequencing is the other classic trap. The principal diagnosis is the condition established after study to be chiefly responsible for the admission, not necessarily the admitting symptom or the most resource-intensive problem. Choosing the wrong principal diagnosis changes the DRG even when every individual code is valid, so DRG questions frequently test sequencing judgment rather than code lookup. When a scenario gives a symptom plus a confirmed underlying cause treated during the stay, the confirmed condition is usually the principal diagnosis — and that choice, not a payment goal, sets the group.