Timing of chest X-ray: by day 7 of symptom onset
Analysis:
(1) The left and right lung are each divided into 3 equal zones (upper, middle, lower), giving a total of 6 zones.
(2) Each zone is graded for the percent lung opacification.
(3) The number of zones with opacification are counted.
overall percent opacification =
= SUM(percent opacification in all 6 zones) / 6
number of zones with opacification =
= (number of zones with percent opacification > 0)
Interpretation:
• minimum overall percent involvement: 0%
• maximum overall percent involvement: 100%
• minimum number of zones with opacification: 0
• maximum number of zones with opacification: 6
|
Percent Total Lung Opacification
|
Disease Status
|
Mortality
|
|
< 5%
|
mild
|
3-5%
|
|
5 to 19.9 %
|
moderate
|
11-13%
|
|
>= 20%
|
severe
|
68-72%
|
|
Number of Zones with Opacification
|
Disease Status
|
Mortality
|
|
0 or 1
|
mild
|
2%
|
|
2 or 3
|
moderate
|
10-11%
|
|
4 to 6
|
severe
|
57-59%
|
Performance:
• The area under the ROC curve for percent total lung opacification is 0.86.
• The area under the ROC curve for zones with opacification is 0.90.
