A Comparison of the Results of Spirometry Performed on a 10-Year-Old

A comparison of the results of spirometry performed on a 10-year-old before and after administration of a bronchodilator evaluates airway obstruction and assesses reversibility. What spirometry result shows significant reversibility and is diagnostic for asthma?

A) Increase in the forced vital capacity (FVC) to a normal value for a 10-year-old
B) Increase in the forced expiratory volume (FEV) 1/FEV ratio from 70% to 85% predicted
C) Increase in the peak flow results of 20% or more
D) Increase of at least 12% in the FEV1