Major Complication and Comorbidity (MCC)

A Major Complication and Comorbidity (MCC) is essentially any serious secondary diagnosis that increases the complexity of a patient's condition. As a result, it also increases the resources required to treat it.

What is a Major Complication and Comorbidity (MCC)?

An MCC is a condition that when combined with the primary diagnosis increases the risk of mortality. It also impacts the resource utilization and the length of hospital stay.

The Centers for Medicare & Medicaid Services (CMS) classifies these conditions under the DRG payment system. Reason? To ensure hospitals are appropriately reimbursed for complex cases.

There is a clear distinction between MCCs and CCs. MCCs are differentiated by their greater impact on patient care and resource demands. While CCs also affect DRG assignment, MCCs result in even higher DRG weights and thus higher payments.

Why Do MCCs Matter in Medical Billing?

MCCs play a key role in:

  • Determining the severity level of a hospital case under the DRG system.
  • Adjusting reimbursement rates to reflect the added care complexity.
  • Encouraging detailed and accurate clinical documentation and coding.
  • Influencing hospital performance metrics, such as case mix index (CMI)

Accurate identification and coding of MCCs ensure fair compensation for hospitals treating the most critically ill patients.

Examples of MCC Diagnoses

Below are some commonly recognized MCCs:

  • Septicemia
  • Acute respiratory failure
  • Stage 4 pressure ulcer
  • Acute renal failure with dialysis
  • Malnutrition
  • Intracranial hemorrhage

These diagnoses must be documented clearly.  They should also be supported by clinical evidence in the patient’s medical record to be coded as MCCs.

How Are MCCs Used in DRG Assignment?

In Medicare's MS-DRG (Medicare Severity-Diagnosis Related Group) system:

  • Each inpatient stay is grouped based on three criteria: the primary diagnosis, procedures, and secondary conditions.
  • The presence of an MCC increases the DRG weigh
  • This adjustment ensures that hospitals are compensated for the added clinical severity and resource utilization.

For example:

  • DRG 193: Simple pneumonia & pleurisy without CC/MCC
  • DRG 192: Simple pneumonia & pleurisy with CC
  • DRG 191: Simple pneumonia & pleurisy with MCC – receives the highest payment due to increased complexity.