HCM530
Case Study 4
Risk Adjustment with Multivariate Techniques (New York)
The state of New York (http://www.health.state.ny.us/nysdoh/consumer/heart/1996-98cabg.pdf) has
reported risk adjusted mortality statistics for coronary artery bypass graft surgery (CABG) for a number
of years, as discussed earlier in the text. New York uses the second major approach to risk adjustment, a
multivariate model. Such models control for different kinds of patient characteristics that are likely to
influence mortality. Table 4.1 reports the multivariate model used to calculate this risk-adjusted
measure. (Textbook Case Study 6.4)
Table 4.1: Multivariable risk factor equation for CABG hospital deaths in New York State in 1998.
Logistic Regression
Patient Risk Factor Prevalence (%) Coefficient P-Value Odds Ratio
Demographics
Age …. 0.0671 <0.0001 1.069
Female Gender 28.92 0.5105 <0.0001 1.666
Hemodynamic State
Unstable 1.32 1.0423 <0.0001 2.836
Shock 0.45 1.8458 <0.0001 6.333
Comorbidities
Diabetes 30.91 0.3607 0.0010 1.434
Malignant Ventricular Arrhythmia 2.228 0.9759 <0.0001 2.654
COPD 15.97 0.5012 <0.0001 1.651
Renal Failure (no dialysis),
Creatinine > 2.5 1.89 0.9213 <0.0001 2.513
Renal Failure requiring Dialysis 1.89 0.9213 <0.0001 5.688
Hepatic Failure 0.10 3.0535 <0.0001 21.190
Severity of Atherosclerotic Process
Aortoiliac Disease 5.42 0.5481 0.0006 1.730
Stroke 7.01 0.4775 0.0016 1.621
Ventricular Function
Ejection Fraction <20 1.77 1.4235 <0.0001 4.151
Ejection Fraction 20-29 7.40 0.8183 <0.0001 2.267
Ejection Fraction 30-39 14.49 0.6186 <0.0001 1.856
Previous Open Heart Operations 5.98 0.6800 <0.0001 1.974
Intercept = -9.4988
C Statistic = 0.793
Case Questions: Answer the case questions, with research from your book, CDC, NIH and other quality sources to determine answers and solutions. You are to write a 2-3 page paper in APA formatting that addresses the following questions. Note: A minimum of two references should be used, which should include your textbook and the CDC, and others that support your responses in your paper. This is a mpaper, so your answer should not be numbered, but rather it should use titles and subtitles.
1. Which factors are supposedly related to CABG morality?
2. Which factors are the most strongly related to CABG mortality?
3. How could one derive an expected mortality rate from the multivariate model?
