Table 1: Hay reference values according to age.

Values of FeNO (ppb), patients ≥ 12 years of age Low Intermediate High
< 25 25 - 50 > 50
Values of FeNO (ppb), patients < 12 years of age < 20 20 - 35 > 35

Source: Dweik RA, et al. [21].