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Background:
The eosinophilic
asthma phenotype
(sputum eosinophils
≥3%) indicates a
good response to
corticosteroids and
TH2
immunomodulators.
Exhaled nitric oxide
(FeNO) is rapidly
measured by portable
devices, and
although it is not a
selective marker of
eosinophilic
inflammation,
several studies have
demonstrated a
strong correlation
with it. We
investigated which
FeNO value was the
best fit with 3%
sputum eosinophils
in asthma patients.
Methods: We
included 129
consecutive,
nonsmoking
asthmatics who
underwent skin
tests, FeNO
quantification (NIOX
MINO), spirometry,
and induced sputum
analysis and
completed the Asthma
Control Test
questionnaire.
Receiver operating
characteristic
curves were
constructed, and
logistic regression
analysis was
performed.
Results:
Symptoms were
detected more
frequently in the
eosinophilic asthma
group, as were
higher airway
obstruction and
sensitivity to
hypertonic saline.
The FeNO cutoff
point of 21 ppb was
the best fit with 3%
sputum eosinophilia.
This value behaved
better among
corticosteroid-naïve
patients
(sensitivity, 97%;
specificity, 58%;
positive predictive
value, 86%; negative
predictive value,
88%) than among
those receiving
corticosteroids
(sensitivity, 81%;
specificity, 25%;
positive predictive
value, 74%; negative
predictive value,
33%).
Conclusion:
FeNO ≥21 ppb is
associated with
airway eosinophilia.
In
corticosteroid-naïve
patients, FeNO <21
ppb enables us to
rule out airway
eosinophilia.
Key words:
Asthma. Nitric oxide
cut point.
Eosinophilic
phenotype. ROC
curves. Sputum
eosinophils. |
