Research Objectives:
Variation in VolumeVolume-Outcome
Relationships for Hospitals and
Surgeons Performing CABG Surgery
Christopher P. Gorton MD, MHSA
Jayne L. Jones MPH
Christopher S. Hollenbeak PhD
David B. Campbell MD
Diane L. Arke MS
„
To describe the variation in riskrisk-adjusted
outcomes for individual surgeons and hospitals
with similar case volumes
„
To examine the association between case
volume and two outcomes, 3030-day mortality
rates and 77-day readmission rates, for surgeons
and hospitals
Pennsylvania Health Care Cost Containment Council
Pennsylvania Health Care Cost Containment Council
Methods
Principal Findings
Isolated CABG surgeries, 2002:
„
16,435 patients; 62 nonnon-federal Pennsylvania
hospitals; 190 surgeons
Retrospective analysis of administrative and
medical record abstracted data reflecting
statewide experience. Generalized estimating
equations (GEE) framework used to account for
the correlations between patients treated by the
same surgeons and at the same hospital.
Pennsylvania Health Care Cost Containment Council
Regression Coefficients
„
„
Wide variation was seen between and within
outcome measures at all volume levels
Extreme mortality observations were
demonstrated across the entire volume spectrum.
Likelihood of patient death within thirty days
decreased as surgeon case volume increased
(adjusted risk ratio [RR] for each 25 case
increment, 0.93; 95% confidence interval [CI],
0.870.87-0.99; P=0.031).
Pennsylvania Health Care Cost Containment Council
Surgeon VolumeVolume-Mortality Scatter Plot
Revised
Model
Coefficient
-0.001
0.000
-0.003
-0.002
p-value
0.0706
0.3099
0.0314
0.0967
Coefficient
-0.001
0.000
-0.004
-0.002
p-value
0.0708
0.3047
0.0045
0.0424
0.08
0.06
7-day
Readmission
0.04
30-day
Mortality
7-day
Readmission
0.02
Initial
Model
Surgeon Case Volume
30-day
Mortality
0.00
Model Parameters
Risk Adjusted 30-day Mortality Rate
Outcome Measure
Hospital Case Volume
0
50
100
150
200
Surgeon Annual CABG Volume, No. of Procedures
Pennsylvania Health Care Cost Containment Council
Pennsylvania Health Care Cost Containment Council
„1
„
With selective referral, predicted lives saved =
23, but 15.9% probability of increased lives lost
0.025
Statewide Mortality Risk Ratio, Observed vs.
Simulation: 1.080 (95% CI: 0.927 to 1.260)
Mortality Rate
„
0.020
Modeled outcomes of 1,000 simulated choices in
each of 8 regions, in which patients of low
volume surgeons were reassigned to surgeons
with midmid-high volumes in the same region
0.015
„
Surgeon Mortality:
Actual vs. Simulated
0.030
Results of Simulated Policy of Referral
to MidMid-High Volume Surgeons
All Surgeons
Pennsylvania Health Care Cost Containment Council
Pennsylvania Health Care Cost Containment Council
Conclusions
„
For individual consumers, surgeon volume is a
weak predictor of mortality and rere-admission
„
Large scale implementation of a selective CABG
referral policy has nonnon-trivial probability of
negative public health impact
„
Lack of correlation among four studied outcome
measures highlights need for multimulti-dimensional
performance measurement
0.010
0.000
0.005
Density
0.015
0.020
Probability Distribution of Predicted
Lives Saved by Simulated Policy
-100
-50
0
50
100
150
High Volume Surgeons
Predicted Lives Saved
Pennsylvania Health Care Cost Containment Council
Pennsylvania Health Care Cost Containment Council
„2