CDIP DRG Optimization and Case Mix Index 1 — Questions and Answers
Question 1: What is the Case Mix Index (CMI) and why is it significant to a CDI program?
- A measure of patient satisfaction used to benchmark hospitals
- A numeric value reflecting the average relative weight of all MS-DRGs billed by a hospital, indicating resource use and complexity (Correct answer)
- The total number of diagnoses coded per discharge
- A payer-specific metric used only for Medicaid reimbursement
Correct answer: A numeric value reflecting the average relative weight of all MS-DRGs billed by a hospital, indicating resource use and complexity
CMI is calculated by averaging the relative weights of all MS-DRGs assigned during a period; a higher CMI reflects a more complex patient population and directly impacts Medicare reimbursement and quality benchmarks.
Question 2: Under the MS-DRG system, which of the following MOST directly increases a DRG's relative weight and associated reimbursement?
- Documenting and coding a complication or comorbidity (CC) or major complication or comorbidity (MCC) (Correct answer)
- Increasing the patient's length of stay beyond the geometric mean
- Assigning a larger number of secondary diagnoses regardless of clinical specificity
- Selecting a procedure code from a higher-cost DRG family
Correct answer: Documenting and coding a complication or comorbidity (CC) or major complication or comorbidity (MCC)
CCs and MCCs are secondary diagnoses that, when documented and coded, move a case from a base DRG to a higher-weighted DRG, resulting in greater reimbursement to reflect the increased resource use.
Question 3: A CDI specialist is reviewing a record where the principal diagnosis is listed as 'chest pain.' The physician also documented acute NSTEMI confirmed by troponin elevation. What CDI action is MOST appropriate?
- Leave the principal diagnosis as chest pain since it was the reason for admission
- Query the physician to clarify whether the NSTEMI should be the principal diagnosis (Correct answer)
- Code both diagnoses as co-principal diagnoses
- Report the discrepancy to compliance and take no further action
Correct answer: Query the physician to clarify whether the NSTEMI should be the principal diagnosis
Per UHDDS guidelines, the principal diagnosis is the condition established after study to be chiefly responsible for the admission; the confirmed NSTEMI likely meets this definition and warrants a query for clarification.
Question 4: Which of the following secondary diagnoses would qualify as a Major Complication or Comorbidity (MCC) under the MS-DRG system?
- Mild persistent asthma, well controlled
- Acute respiratory failure (Correct answer)
- Essential hypertension
- Vitamin D deficiency
Correct answer: Acute respiratory failure
Acute respiratory failure is classified as an MCC because it significantly increases the resources needed to treat the patient compared to the principal condition alone, reflecting its high severity.
Question 5: A hospital's CMI drops significantly over two quarters. After ruling out a change in patient population, which CDI-related factor is MOST likely contributing?
- Increased ED visit volume
- Underreporting of CC/MCC diagnoses due to documentation gaps (Correct answer)
- Higher readmission rates
- Decreased length of stay
Correct answer: Underreporting of CC/MCC diagnoses due to documentation gaps
A CMI decline without a population shift typically indicates that CC/MCC conditions are not being documented and coded, resulting in cases falling into lower-weighted base DRGs.
Question 6: In the MS-DRG grouping logic, what happens when NEITHER a CC nor an MCC is present for a condition that has a three-way DRG split?
- The case is automatically denied by Medicare
- The case groups to the base (lowest-weight) DRG without CC/MCC (Correct answer)
- The grouper assigns the MCC DRG by default
- The principal diagnosis is changed to reflect the highest-acuity DRG
Correct answer: The case groups to the base (lowest-weight) DRG without CC/MCC
When no qualifying CC or MCC is coded, the MS-DRG grouper assigns the case to the lowest-weight base DRG in the three-way split, reducing reimbursement.
CDIP DRG Optimization and Case Mix Index 1
What is the Case Mix Index (CMI) and why is it significant to a CDI program?