The Respiratory Therapist Is Assisting the Pulmonologist on a Methacholine

The respiratory therapist is assisting the pulmonologist on a methacholine challenge. After inhalation of the fourth concentration of methacholine, the FEV₁ decreases by 12%. What should the therapist suggest at this time?

A) Stop the challenge because a drop in the FEV₁ is consistent with a positive test.
B) Stop the challenge because only four concentrations are delivered.
C) Administer one more concentration to confirm that FEV₁ drop is in fact 12%.
D) Continue administering methacholine until FEV₁ decreases 20%.