Usefulness of reference values for spirometry
Lung diseases are very prevalent. Apart from respiratory symptoms they are associated with obstructive and/or restrictive ventilatory defects, which must be assessed with lung function tests. Usually results of previous spirometric tests are unavailable, so that it is difficult to judge whether the present results are within the normal range for that subject. In such circumstances reference values may be useful, i.e. equations used to predict ventilatory function of
- a healthy subject of
- the same length,
- gender and
- ethnic group.
The best reference value, however, is a measurement performed in a patient in a clinically optimal condition.