Before knowing what exactly, Exhaled Nitric Oxide test is first we there is a need to know is for what purpose is this test conducted. Well nitric oxide test is conducted or useful for screening and diagnosing asthma. The ENO testing is quite reliable and popular and is reproducible, internationally approved and one of the convenient marker of airways inflammation in both school-aged and adults.

Now let us get an insight into how ENO works for the purpose of diagnosing asthma. Well the patient is made comfortably settled without any nose clip and exhales at a steady level for 4-6 seconds. The very test of nitric oxide is repeated for three times to ensure the accurate values. With a nose attachment on the nose analyzer, the nasal oxide levels can be measured exactly. the result indicates that the normal adult will have nitric oxide levels exhaled from the mouth between 5 and 20 ppb, whereas a asthmatic will have much higher results i.e. around 50ppb.

Many of the good studies indicated that it is not always appropriate that the asthma control is necessarily reflected by self-reported symptoms and spirometry as the airway inflammation may remain constant at different times of the day and night  without showing any learning effect so in that case objective test like nitric oxide test well correlate with asthma.

 Hence, it would be right to say that screening or diagnosing individuals using nitric Oxide test can help tailor the treatment and dosing especially to the patients with chronic disease.