Redefining CDI Success: Beyond Case Mix Index

About CMI

Not too long ago, the expectation of an effective CDI program was tightly aligned with CMI increases. This is not surprising when you consider a few points:  

1. An effective CDI program can indeed increase CMI, especially in the long term through accurate reporting of patient severity.  

2. CDI programs typically report to finance/revenue cycle departments, to which CMI is a closely monitored metric.  

Before we delve deeper into this topic, let’s first cover a few CMI basics. According to CMS.gov, the Case Mix Index represents a hospital's average diagnosis-related group (DRG) relative weight for a given time period. It’s calculated by summing the DRG weights for all Medicare discharges and dividing them by the number of discharges. The CMI reflects the clinical complexity and resource needs of all the patients in the hospital. A CMI higher than 1.00 indicates a more complex and resource-intensive caseload.  

So why do so many "new age" CDI subject matter experts and leaders get uneasy when CDI performance or effectiveness is measured primarily by CMI? Here are a few hypotheses as to why this metric/measure causes frustration with so many:  

1. Quality Metrics:  

Quality performance metrics are more prevalent in healthcare, with incentives and penalties tied to them. Thus, there is an increased need for the capture of the true severity of illness for a patient population, since this impacts risk-adjusted expected values in many quality performance metrics. Oftentimes, this means generating a documentation query to providers even when it does not impact DRG severity assignment and subsequent reimbursement. This is the case with APR-DRG groupings, where diagnoses are assigned a Severity of Illness (SOI) and Risk of Mortality (ROM) score or weight.

2. Multiple Influencers on CMI:  

CMI can be affected by many other variables besides improved severity documentation alone, like:  

• The random mix or types of patients that get admitted during a given month.  

• The hospital expands certain service lines, bringing in higher relative-weight patients (e.g., the number of tracheostomies, ventilated patients, transplants, and other surgical procedures during a given time period.)

• COVID volumes have changed, with the patient population now presenting higher severity cases, and COVID is still being reported as an MCC.

• The hospital implements new technology such as CAC technologies or electronic medical records.  

• Coding accuracy, productivity, and adherence to coding guidelines: Increased productivity demands on coders could affect the accurate coding and efficiency of coders.

• Annual updates to CMS’s Table V, inclusive of relative weight adjustments can impact the reported CMI.

3. Measuring CDI Program Performance

CMI alone will not be a very good indicator of the performance of your CDI program at your hospital, nor actual severity documentation performance, especially in the short term. Additionally, many programs have a limited scope and cannot consistently review all cases at all times. So how do we get down to actual program performance then?  

Many suggest carving out the factors that influence the fluctuations in CMI not related to improved documentation and then monitoring other metrics as well. These include:  

• Review rates  

• Query rates  

• Physician response rates  

• Physician agreement rates

• Capture Rates  

These are good suggestions but can become complicated. It would take an astute CDI leader to be able to make correlations between actual changes in documentation performance and the above-listed metrics, and then present a solid case based on the data collected versus the actual point increase or decrease in CMI.  

The Physician’s Perspective

To add to the confusion, let’s consider the perspective of physicians at the bedside. Which of these metrics truly reflects their documentation performance according to industry guidelines and regulations? Does a low query rate for difficult orthopedic surgeons indicate better documentation compared to a responsive hospitalist? A lower review rate could simply mean a CDS was unavailable for a few weeks or was dealing with more complex cases requiring additional time.

It is crucial to define high-quality severity documentation performance not just for your program, which may have a limited scope, but for the entire organization. Then, identify the most impactful component of that definition and apply a metric to it.  

At ClinIntell, we believe the best long-term approach to supplement traditional CDI efforts is for physicians to document diagnoses based on approved definitions when patients meet specific clinical criteria. This ensures that the severity of illness is accurately captured, not just for patients within the scope of the CDI program but for all patients they care for.

While accurate documentation of clinical conditions by physicians drives CMI, using CMI as a performance metric may not resonate with physicians as effectively as it does with your CFO. Many CMOs and physician leaders have a limited understanding of CMI and its relevance to accurately portraying severity in patient charts. This is understandable, as CMI 101 is not part of the medical school curriculum.  

Distinguishing Performance Metrics

We must make a clear distinction between what we are trying to measure. Is it:  

1. CDS effectiveness and productivity?  

2. Overall effectiveness of the CDI program alone?  

3. Actual physician documentation performance?  

4. Physicians’ participation in the initiative as a whole?  

From the CFO’s point of view, the emphasis should rightfully be on overall CMI. Any fluctuations that require further attention should result in an efficient root cause analysis process. At that point, the metrics that speak specifically to the CDI program's efficiency could be factored in.

From the CDI leader’s standpoint, it will be necessary to monitor metrics to ensure that the program is running efficiently and effectively. The physician leader should be concerned with physician participation in the program and with overall documentation performance.

For individual physicians, the focus should be on improving their documentation performance on specific clinical conditions they can impact and striving to reduce the number of queries received over time.

Conclusion

While CMI should not be entirely disconnected from severity documentation performance, unexpected CMI changes should prompt a thorough analysis of CMI and CDI program metrics. These metrics might reveal areas of underperformance among CDSs or physicians.   

Key takeaways include:  

1. Avoid linking CDI program efficiency solely to CMI.  

2. Do not use CMI to measure physician documentation performance (there are patient-mix factors out of a physician’s control that can cause significant month-to-month fluctuation).  

3. Clearly define, measure, and familiarize yourself with the necessary metrics to enable you to be successful in supporting the CDI efforts at your organization, from the CDI manager to the physician at the bedside.  

In any case, regardless of the degree to which you link CMI to CDI, we can all agree that a CDI program is only as effective as its weakest link.