FeNO may help to diagnose cough variant asthma,DR.D.K.JHA,M.D.
Tuesday, November 12th, 2019Asthma,only as cough
Asthma is a leading cause of respiratory morbidity all over the world whether it be adult or children.In cough variant asthma,patients have only symptom of troublesome cough for a long period.They do not complaint of tightness of chest,difficulty in breathing,or wheezing any time in the course of their illness.On CHEST auscultation,there is no adeventitious sound in the form of wheeze.This type of cough presents a difficulty in front of treating physician for the accurate diagnosis.It may be asthma or other diagnosis which needs meticulous investigations.It is also difficult to convince to patients or parents that it may be asthma,because there is a common belief among patients and parents that asthma means difficulty in breathing.On the other hand,spirometry,which is a goldstandard diagnostic test for asthma, done on such type of asthma patients are usually normal.
FeNO(Fractional excretion of nitric oxide) is measured by a portable machine,which is hand held and subject is asked to exhale through the mouth piece connected to a hand held device.The measurement is in part per billion(ppb).The normal and abnormal levels have been validated in adults,not in children.But its level when it is high,well correlates with eosinophilic inflammation of airways in children and it can be performed easily in school going children.
In a study ,32 patients with an average age of 42.5 years were included.All had only cough for a long period(chronic cough),normal blood eosinophil count,normal chest X-Ray,normal spirometry results but abnormal ACT(Asthma control test) and positive skin prick test for environmental antigens.9 healthy persons were included for control with the mean age of 47 years.FeNO measurements were taken with the help of FeNO analyser.
FeNO were significantly elevated with the mean value of 64.4ppb in 91%(n29) of patients.The normal cut off value for adults is 25ppb.In healthy controls,the mean value measured was 16ppb.
REFERENCES:Nsouli T, Diliberto N, Nsouli S, Zamora S, Nsouli A, Bellanti J. Lack of concordance between FeNO and spirometry in patients with chronic cough. Presented at: American College of Allergy, Asthma, & Immunology Annual Scientific Meeting 2019; November 7-11, 2019; Houston, TX. Abstract A202