In many cases, patients with asthma will present with normal spirometry, consistent with the variable nature of the condition. In other words, when the patient is asymptomatic, spirometry is normal. Evidence of airflow obstruction is only detected in the majority of cases when the patient is symptomatic. It’s important to remember that a normal spirometry does not rule out asthma. Most patients with mild or moderate asthma don’t have obstructive spirometry in between periods of having symptoms.