Final answer:
An elevated FeNO is most commonly associated with asthma, as it indicates eosinophilic airway inflammation, which is characteristic of this condition. Option 1 is correct.
Step-by-step explanation:
You would suspect an elevated Fractional exhaled Nitric Oxide (FeNO) in patients with asthma. FeNO is a biomarker of airway inflammation, and its levels are known to be higher in individuals with allergic asthma due to the presence of eosinophilic airway inflammation.
By comparison, in conditions like bronchitis, smokers, and sarcoidosis, FeNO levels might not be elevated. In fact, smokers often have decreased FeNO levels due to the inhibitory effect of smoke on the enzyme that produces nitric oxide.
Likewise, sarcoidosis, being a granulomatous disease, does not typically result in elevated FeNO levels. Therefore, out of the options provided, asthma is the condition most likely to be associated with an elevated FeNO.