Background
Discussion
Disadvantages of the VLAD
Risk adjusted cumulative sum (RA-CUSUM) approach
Comparison of RA-CUSUM and VLAD approaches
Scenario: expected, actual mortality rate | Method | Proportion of chart exceeding the control limit at patient | ||||||
---|---|---|---|---|---|---|---|---|
10 | 25 | 50 | 75 | 100 | 150 | 200 | ||
1: 5 %, 5 % | VLAD | 0.01 | 0.02 | 0.02 | 0.02 | 0.03 | 0.02 | 0.03 |
RA-CUSUM |
0.00
|
0.00
|
0.01
|
0.01
|
0.02
|
0.02
| 0.03 | |
2: 1 %, 2 % | VLAD |
0.01
|
0.08
|
0.08
| 0.06 | 0.14 | 0.18 | 0.21 |
RA-CUSUM | 0.00 | 0.01 | 0.05 |
0.08
|
0.15
|
0.22
|
0.32
| |
3: 10 %, 10 % but with 6 deaths in a row patients 94–99 | VLAD | 0.02 | 0.02 | 0.02 | 0.02 | 0.32 |
0.01
|
0.01
|
RA-CUSUM |
0.00
|
0.00
|
0.00
|
0.01
|
1.00
| 0.37 | 0.22 | |
4: 10 %, 10 % for first 100 patients, then 12.5 % | VLAD | 0.01 | 0.01 | 0.02 | 0.02 | 0.02 | 0.06 | 0.07 |
RA-CUSUM |
0.00
|
0.00
|
0.01
|
0.01
|
0.01
|
0.07
|
0.12
|