Comparing reference values - 1
The
predicted FEV1/(F)VC ratio varies
little among different authors, and is for practical purposes independent
of racial group. However, the level of the predicted FEV1
tends to vary appreciably. The best way to assess which prediction
equation best fits the population that you are going to work with
is to investigate how well an equation fits a representative sample
of a healthy, nonsmoking population in your area. However, this
is usually a costly and large undertaking well beyond your means.
It is then common practice to use regression equations derived from
studies of large populations that resemble the population in your
environment. Since the FEV1/FVC
ratio does not differ much among authors, it is probably sufficient
to compare predicted FEV1.
Incorporated into the SpirXpertsoftware is a considerable number of widely used regression equations. This allows the user to compare the predicted FEV1 according to various authors. Arbitrarily they are compared to a set of default prediction equations for adults and for children/adolescents.
There are occasionally considerable differences in predicted FEV1. The greatest discrepancies occur in children and adolescents. This is due to the fact that the simplest prediction models, which predict FEV1 and FVC only as a function of standing height over a wide age range (such as FEV1 = a·Hk or FEV1 = eH·k) fail to take into account the change in body proportions that occur during growth from child to adult. This is best illustrated if one uses a relative rather than an absolute scale, as shown on the next page.
See also:
Software download
Predicted values for FEV1, FVC and FEV1%FVC in adults
Predicted values for FEV1, FVC and FEV1%FVC in children and
adolescents