Monitoring the quality of cardiac surgery based on three or more surgical outcomes using a new variable life-adjusted display.
OBJECTIVE
The traditional variable life-adjusted display (VLAD) is a graphical display of the difference between expected and actual cumulative deaths. The VLAD assumes binary outcomes: death within 30 days of an operation or survival beyond 30 days. Full recovery and bedridden for life, for example, are considered the same outcome. This binary classification results in a great loss of information.


METHODS
Although there are many grades of survival, the binary outcomes are commonly used to classify surgical outcomes. Consequently, quality monitoring procedures are developed based on binary outcomes. With a more refined set of outcomes, the sensitivities of these procedures can be expected to improve.


METHODS
A likelihood ratio method is used to define a penalty-reward scoring system based on three or more surgical outcomes for the new VLAD. The likelihood ratio statistic W is based on testing the odds ratio of cumulative probabilities of recovery R. Two methods of implementing the new VLAD are proposed.


METHODS
We accumulate the statistic W-W¯R to estimate the performance of a surgeon where W¯R is the average of the W's of a historical data set. The accumulated sum will be zero based on the historical data set. This ensures that if a new VLAD is plotted for a future surgeon of performance similar to this average performance, the plot will exhibit a horizontal trend.


RESULTS
For illustration of the new VLAD, we consider 3-outcome surgical results: death within 30 days, partial and full recoveries. In our first illustration, we show the effect of partial recoveries on surgical results of a surgeon. In our second and third illustrations, the surgical results of two surgeons are compared using both the traditional VLAD based on binary-outcome data and the new VLAD based on 3-outcome data. A reversal in relative performance of surgeons is observed when the new VLAD is used. In our final illustration, we display the surgical results of four surgeons using the new VLAD based completely on 3-outcome data.


CONCLUSIONS
Full recovery and bedridden for life are two completely different outcomes. There is a great loss of information when different grades of 'successful' operations are naively classified as survival. When surgical outcomes are classified more accurately into more than two categories, the resulting new VLAD will reveal more accurately and fairly the surgical results.
Department of Statistics and Applied Probability, National University of Singapore, 6 Science Drive 2, 117546, Republic of Singapore.
Fah Fatt
FF
Gan
Department of Statistics and Applied Probability, National University of Singapore, 6 Science Drive 2, 117546, Republic of Singapore.
Xu
X
Tang
Department of Statistics and Applied Probability, National University of Singapore, 6 Science Drive 2, 117546, Republic of Singapore.
Yexin
Y
Zhu
Department of Statistics and Applied Probability, National University of Singapore, 6 Science Drive 2, 117546, Republic of Singapore.
Puay Weng
PW
Lim
D006348:Cardiac Surgical Procedures / Q000009:adverse effects / Q000401:mortality*; D002983:Clinical Competence; D006801:Humans; D008485:Medical Audit / Q000379:methods; D010043:Outcome and Process Assessment, Health Care / Q000379:methods*; D018570:Risk Assessment; D015996:Survival Rate
Parsonnet score; likelihood ratio statistic; multiple surgical outcomes; quality monitoring; quality of cardiac operations; risk adjustment