Introduction
There are a few fundamental concepts that are applicable in deciding what is a good test with respect to estimating values that represent a subject's maximal effort. One important consideration is the context or use of the test results when establishing the grading system used to assign grades. Specifically, a grading system used to assign grades as feedback to a technician for performance improvement would be different from a grading system used to assign grades to determine whether a test can be interpreted for clinical purposes. Also, a grading system used to assign grades to determine whether a subject is included in a study must consider the possible resultant bias that may be introduced (age and disease are know to correlation with quality measures) if large numbers of subjects with less than a perfect quality test are excluded.
In general, FVC and FEV1 grades are assigned based on the question: Do the FVC and FEV1 values represent likely maximal values to within 150 ml? All information and curves available should be used to make this determination, even less than acceptable or partially acceptable curves.
1. The most common reason for low, or sub-maximal, values is an incomplete inhalation. An incomplete inhalation affects both the FVC and FEV1. One of the most important quality components is whether a complete inhalation likely occurred; and test repeatability is one of the best determinants of a complete inhalation. Formal measures of repeatability are made by comparing the FVC and FEV1 values from individual curves. However, the reviewer can, and should use, the repeatability of the shapes of the curves to determine if a maximum inhalation or maximal effort has occurred.
2. The quality of the curve after the first second does not affect the FEV1. So, the FEV1 may be derived from a curve with early termination or other end of test failures.
3. The flow-volume curve is very useful in evaluating the initial portion of the effort but sometimes may over-emphasize curve quality with respect to the FEV1. Specifically, because of the negative effort dependency of the FEV1, curves with low peak flows may be acceptable. The maximal FEV1 occurs for some subject at approximately 85% to 90% of the highest observed peak flow. Thus, the FEV1 on curves with peak flows as low as 75% of the maximal peak flow will often provide a repeatable FEV1. As long as the extrapolated volume does not exceed the limit of 150 ml or 5% of the FVC, whichever is greater, these curves may be used.
4. The objective is to accurately estimate a subject's maximal effort values. Therefore, rejected or unacceptable curves may be used to validate a test, particularly when there are less than three acceptable curves. Rejected or unacceptable curves, particularly those rejected because of large extrapolated volumes, low peak flows, or coughs, may be used to determine if maximal inhalation occurred -- important information for assessing the quality of both the FVC and FEV1.
Tests with questionable plateaus or early termination
ID 11950 (Number 17), Computer Grade QFVC=F, QFEV1=A
ID 11166 (Number 12), Computer Grade QFVC=F, QFEV1=A
ID 11061 (Number 10), Computer Grade QFVC=F, QFEV1=A
ID 14070 (Number 41), Computer Grade QFVC=F, QFEV1=A
ID 16770 (Number 70), Computer Grade QFVC=A, QFEV1=A
ID 14904 (Number 50), Computer Grade QFVC=F, QFEV1=C
ID 16901 (Number 71), Computer Grade QFVC=F, QFEV1=A
ID 18095 (Number 80), Computer Grade QFVC=F, QFEV1=A
ID 20874 (Number 96), Computer Grade QFVC=F, QFEV1=A
Tests with poor initial efforts
ID 10074 (Number 3), Computer Grade QFVC=A, QFEV1=B
ID 1010 (Number 4), Computer Grade QFVC=A, QFEV1=F
Tests that are not repeatable
ID 13456 (Number 32), Computer Grades QFVC=F, QFEV1=F
ID 13634 (Number 34), Computer Grade QFVC=F, QFEV1=C
ID 14272 (Number 43), Computer Grade QFVC=C, QFEV1=A
ID 1457 (Number 46), Computer Grades QFVC=A, QFEV1=D
Tests where rejected or unacceptable curves are used to validate a test
ID 2126 (Number 104), Computer Grades QFVC=F, QFEV1=F
ID 17720, Computer Grades QFVC=D, QFEV1=A
ID 18738, Computer Grades QFVC=C, QFEV1=D
ID 10986 (Number 9), Computer Grades QFVC=C, QFEV1=B
ID 14550 (Number 44), Computer Grades QFVC=F, QFEV1=A (Cough)