Which metric best reflects the impact of CDI interventions on documenting patient complexity over time?

• A. ED wait times are best for evaluating CDI interventions.
• B. Readmission rate is the sole indicator of CDI success.
• C. Case Mix Index trend over time best reflects the impact of CDI interventions on documenting patient complexity.
• D. Average medication cost per patient.

Answer: (C)

The main idea is that CDI efforts aim to capture a more complete picture of patient complexity in documentation. The Case Mix Index (CMI) trend over time best reflects this, because CMI combines the inpatient case weights assigned to diagnoses and procedures. When CDI interventions succeed, more severe or additional comorbid conditions get documented and coded, which increases the average DRG weight and raises the CMI. Tracking this metric over multiple periods shows whether the improvement in documentation is sustained and translates into a higher, more accurate reflection of patient complexity.

Other metrics focus on different outcomes. ED wait times measure throughput and access, not documentation quality. Readmission rate is influenced by many factors beyond coding and documentation. Average medication cost per patient can fluctuate for reasons unrelated to how well complexity is documented, such as formulary changes or practice patterns. So the trend in Case Mix Index most directly indicates how well CDI interventions are capturing patient complexity over time.