| Table
7: |
|
Example
of Criteria for Assessing the Severity of Abnormalities
|
| A.
Normal: The test is interpreted as "within normal limits"
if both the VC and the FEV1/VC ratio ar in the normal range. |
| B.
Obstructive abnormality: This is interpreted when the FEV1/VC ratio
is below the normal range. The severity of the abnormality might be
graded as follows: |
|
"May
be a physiological variant"
|
%
Pred FEV1 > 100
|
|
"Mild"
|
%
Pred FEV1 < 100 and > 70
|
|
"Moderate"
|
%
Pred FEV1 < 70 and > 60
|
|
"Moderately
severe"
|
%
Pred FEV1 < 60 and > 50
|
| "Severe" |
%
Pred FEV1 < 50 and > 34 |
|
|
C. Restrictive
abnormality: This is most reliably interpreted on the basis of TLC.
If this is not available, one may interpret a reduction in the VC
without a reduction of the FEV1/VC ratio as a "restriction
of the volume excursion of the lung." The severity of the abnormality
might be graded as follows:
|
| Based
on the TLC |
|
"Mild"
|
%
Pred TLC < LLN but > 70
|
|
"Moderate"
|
%
Pred TLC < 70 and > 60
|
|
"Moderately
severe"
|
%
Pred TLC < 60
|
|
| Based
on spirometry |
|
"Mild"
|
%
Pred VC < LLN but > 70
|
|
"Moderate"
|
%
Pred VC < 70 and > 60
|
|
"Moderately
severe"
|
%
Pred VC < 60 and > 50
|
| "Severe" |
%
Pred VC < 50 and > 34 |
| "Very
severe" |
%
Pred VC < 34 |
|
| Adapted
from reference 6
|