Acceptable alternatives for forced vital capacity in the spirometric diagnosis of bronchial asthma

In patients with advanced obstructive ventilatory disorders, expiration may last for a relatively long time until the end-of-test standards for forced vital capacity (FVC) are satisfied. This may be difficult for both the patient and the technician. The Forced expiratory volume in 3 seconds (FEV3) and Forced expiratory volume in 6 seconds (FEV6) maneuvers are simple, undemanding and easier to perform when compared with FVC; however, their reliability to be used as alternatives for FVC is controversial.

To judge whether FEV3 and FEV6 can be used instead of FVC in detecting airway obstruction in asthmatic patients.

This study was a case-control laboratory-based study.

The study involved 40 known asthmatic patients and 40 apparently healthy, gender- and age-matched controls. Spirometery was used for assessing pulmonary function according to the American Thoracic Society and European Respiratory Society criteria.

A significant difference in the means between the groups was performed using Student's t-test. The receiver operating characteristic (ROC) curves were used to compare efficiency of the studied spirometric measurements on asthma diagnosis.

The mean of FEV3 was not significantly different when compared with the mean of FVC (P = 0.352 for asthmatic patients and P = 0.957 for control group). This was also true when the mean of FEV6 was compared with the mean of FVC (P = 0.805 for asthmatic patients and P = 0.957 for control group). The area under the ROC curves of FEV1/FVC%, FEV1/FEV3% and FEV1/FEV6% were also comparable.

FEV3 and FEV6 are accurate and reliable alternatives for FVC in assessing airway obstruction of asthmatic patients.