1. Why does the computer grade the FVC as an F, when it is apparent (to me) that EOT was reached?
The end of test is not always clean and perfect. A slight (> 30 ml) increase in volume will cancel the plateau achievement if it is not sustained for one second. The EOT definitions link on the site provides a more complete explanation and examples. If you have any comments on the EOT definition link, let me know.
2. There are some curves with accepted EOT and hence FVC, but with slowish starts with some evidence of sub-maximal effort through the test leading to higher FEV than warranted. Should these efforts so as not to over estimate FEV1? Exclusion is tricky, so we need to consider how to handle these efforts.
Exclusion is very tricky which is why the ATS, and later I think, the ATS/ERS-2005 never put that requirement in their recommendations. It has generally been felt that the problem of slightly elevated FEV1 (negative effort dependency) with sub-maximal efforts is less than the potential problems of someone arbitrarily deleting maneuvers. Usually the increase in FEV1 is not much more than the repeatability criterion. The extrapolated volume should detect really slow starts and the time to peak flow is available. The problem with time to peak flow is that it is very instrument dependent, it sometimes does not work, and no data are available for setting a limit. In my experience in teaching and reviewing tests, we have significant problems getting good test and I think having folks judging and rejecting curves based on their determination of a sub-maximal effort would be problematic.
3. What are the definitions of PEF time and Low PEF?
PEF time calculations are very dependent on the spirometer. The ATS/ERS-2005 has not established any particular cutoff value for an acceptable curve and I provide it for information purposes. PEF Time is the time it takes to reach peak flow. The cutoff used for the analysis in this effort is 120 milliseconds.
A low peak flow is indicate for any curve that has a peak flow less than 20% of the largest observed peak flow.
4. There are frequently curves without a maximal effort throughout the maneuver; should these be defined as acceptable or results used to determine the best values?
The shape of curves, in terms of whether it is acceptable, is more of a judgment than a technical measurement that can be made. So, judgment of good/bad curves should be at the discretion of the reviewer. Sometimes sub-maximal efforts will have the largest FEV1 and whether those curves should be excluded is controversial. Also, the result of including curves with poor effort should have no impact on the FVC and FEV1 values since they would be lower and correspondingly not reported since the largest values are reported. I have arbitrary chosen to provide this curves to the reviewer for consideration in the interest of not providing information that I have arbitrary chosen not to provide to reviewers.
5. Why are grades frequently differ between reviewers?
The grades you see are the computer determined grades, and will probably be lower, but sometimes than your grades. These grades are for information purposes. My grades should not be available to reviewers yet to avoid bias but can be if you wish. I will see if I can add the capability of seeing your comments after they are submitted.
Curves are either acceptable or unacceptable and only the tests overall is provided a grade. Individual curves are not assigned a specific grade.
This is even more complicated by the fact that some curves are unacceptable for consideration for determining the best values (those with coughs during the first second and those with large extrapolated volumes). In contrast, some curves are unacceptable in terms of counting towards the number of acceptable curves, but CAN be used to derived the best values (curves with early termination, etc.). There are a few curves that I as a reviewer have marked as unacceptable but not many.
The grades are for the test and there is a separate grade for FVC and FEV1. The computer determined values for FVC and FEV1 test grades are based on the number of acceptable curves and the repeatability of the FVC and FEV1 as described in our definitions.
Perhaps some confusion arose from the definition of an incomplete inhalation: "For FVC and FEV1 grades calculations, an acceptable curve's FVC or FEV1 should not differ by more than 300 mL (250 mL) from the largest observed FVC or FEV1, otherwise it is considered unacceptable due to an incomplete inhalation." This sentence would probably be clearer if the phrase "For FVC and FEV1 grades calculations" was omitted. This definition was intended to be a definition for the vague unacceptable curve term "incomplete inhalation." So, there is a separate comparison of each curves values with the largest FVC and FEV1 values to determine if the curve has an "complete inhalation" and there an acceptable curve.
In my opinion, the individual reviewers can use whatever information is available to determine the FVC and FEV1 grades. Information from unacceptable and acceptable curves can be used. For example, if there are several curves with large extrapolated, it may be that the FVCs from these curves can be used to help validate the one or two acceptable curve FVCs.
Similarly, if there technically no plateau but the curve has an "obvious" plateau, the reviewer could judge the curve acceptable for determining the number of acceptable curves. There were many tests where I felt there was an adequate plateau where the computer did not technically find a good end of tests. Therefore some test grades were elevated to "C" that the computer labeled as an "F".
Concerning curves without a computer determined plateau, the values from these curves can still be used. The reviewer must judge whether the computer determined plateau was accurate or if the subject obviously had completed his/her exhalation. This is probably one area where there will be the most disagreement. You might want to look at the EOT definition page I created for a better explanation of the issues: End of Test Definition