Abstract

BACKGROUND: Asthma is characterized by variable and reversible expiratory airflow limitation. Thus, it is logical to use the change in FEV₁ in response to a bronchodilating drug (?FEV₁BDR) as a diagnostic tool. An increase of =12% and =200mL from baseline FEV₁ has often been considered diagnostic.

AIM: To evaluate the historical development of the diagnostic cut-off-levels in ?FEV₁BDR for adults as well as the evidence behind these recommendations. 

METHODS: To find out how the ?FEV₁BDR as a diagnostic tool in adult asthma has been characterized, we searched studies from the reference lists of all the main statements, reports and guidelines concerning interpretation of spirometry and management of asthma. Additionally, few recent studies were included.

RESULTS: Very limited amount of evidence of the ?FEV₁BDR among healthy population and even fewer asthma patient studies were found. In healthy persons, the reported upper 95^th percentile levels vary for absolute ?FEV₁BDR between 240-320 mL, for relative ?FEV₁BDR calculated from baseline FEV₁ 5.9-13.3% and ?FEV₁BDR calculated from predicted FEV₁ 8.7-11.6%. However, the absolute and percentage ?FEV₁BDR values calculated from baseline FEV₁ are dependent on age, gender, height and degree of airway obstruction. Thus, the use of ?FEV₁BDR calculated from predicted FEV₁ might be more appropriate.

CONCLUSIONS: Not enough data exist to assess the sensitivity or specificity of any of the cut-off-levels of ?FEV₁BDR to differentiate asthma from healthy subjects or other lung diseases. Further studies are urgently needed.