Patient selection: stable COPD
Parameters:
(1) body mass index in kg per square meter
(2) WBC count in 10^9/L
(3) history of severe exacerbation
(4) post-bronchodilator FEV1 as percent of predicted
(5) number of comorbidities (CHF, diabetes, GERD, asthma)
(6) COPD Assessment Test (CAT) score, from 0 to 40
points for CAT score =
= 2.5 * (CAT score)
|
Parameter
|
Finding
|
Points
|
|
body mass index
|
< 21 kg per sq m
|
21.4
|
|
|
>= 21 kg per sq m
|
0
|
|
WBC count
|
< 10 * 10^9/L
|
0
|
|
|
>= 10 * 10^9/L
|
15.8
|
|
history of severe exacerbation
|
no
|
0
|
|
|
yes
|
34.6
|
|
FEV1
|
>=80 percent of predicted
|
0
|
|
|
50 to 79 percent
|
27.7
|
|
|
30 to 49 percent
|
50.4
|
|
|
< 30% of predicted
|
65.4
|
|
number of comorbid conditions
|
0
|
0
|
|
|
1
|
13.5
|
|
|
2
|
33.8
|
|
|
3 or 4
|
68.4
|
total score =
= SUM(points for all of the parameters)
Interpretation:
• minimum score: 0
• maximum score: 305.6
• The higher the score the greater the risk of a severe exacerbation.
value of X =
= (-0.0000653 * ((score)^2)) + (0.04133 * (score)) - 3.525
probability of a severe exacerbation in the next 5 years =
= 1 / (1 + EXP((-1) * X))
Performance:
• The area under the ROC curve is 0.74.
