At what FEV1/FVC ratio should additional evaluation be required?

The FEV1/FVC ratio is a key measure in respiratory physiology used to assess lung function. An FEV1/FVC ratio of 65% is significant in evaluating obstructive lung disease. When this ratio falls below the threshold of 70%, it indicates the potential for airflow obstruction, which warrants further examination to differentiate between various types of pulmonary conditions.

A ratio of 65% suggests that the individual might experience a reduction in airflow compared to healthy values, which typically hover around 70% to 80% for adults. Consequently, when the ratio reaches this level, it necessitates additional testing, such as bronchodilator reversibility testing or imaging, to fully understand the patient's lung function and to properly diagnose any underlying conditions, such as chronic obstructive pulmonary disease (COPD) or asthma.

Lower cutoff values—such as those in the other choices—are generally regarded as less critical thresholds for additional evaluation, as 70% is often the standard reference. Therefore, identifying 65% specifically highlights a need for a deeper investigation into lung health.