Usefulness of lung function assessment
Spirometric tests are performed on a large scale with different objectives in mind, e.g.:
- Additional information to help establish a clinical diagnosis in a patient.
- Assess the prognosis in a patient. The FEV1 has been so well studied that it is generally accepted that a low value, or a rapid decline, or large variability, is associated with an unfavorable prognosis and high morbidity. In COPD a low FEV1 is usually observed in subjects in their forties or older.
- Assess whether disease is present at an early stage, i.e. prior to overt clinical disease.
- Assist in quantifying the severity of airway disease.
- Assess the effect of therapy, such as corticosteroids, bronchodilators, but also their toxicity, for example in patients receiving cytostatic drugs, which may induce a restrictive ventilatory defect.
- Delineating risk factors, e.g. the odds of developing future respiratory disease such as bronchial hyperresponsiveness, which may be regarded as a risk factor in various professions, or operative risks.
- Monitoring whether the pattern of lung growth or aging is normal. This is mostly done by comparing the results of repeated investigation in one person with cross- sectional data; as we shall see assessing normal individual growth from comparison with cross- sectional data is fraught with hidden dangers.