Reference values play an important role in establishing
whether, in an individual, measured volumes fall
within a range to be expected for a healthy person of the
same sex, similar stature, age, and other characteristics.
Hence, reference values should be chosen that are appropriate
to the person being investigated. Ideally, the reference
values should be consistent; in the context of this
paper, it implies that predictions for the various lung volumes
have been derived from the same reference population,
with the same techniques. Comparing measured
with reference values is fraught with difficulties, as it
may lead to disease going undetected. This is because
the scatter in predicted values is sufficiently large to
allow a sick person to lose, e.g. much of his total lung
capacity (TLC), whilst still remaining in the range observed
in comparable healthy persons. In addition, measurements
in an "abnormal range" are not diagnostic of a
specific disease, as many diagnostic entities may cause