Diagnostic accuracy of fractional exhaled nitric oxide in predicting cough variant asthma and eosinophilic bronchitis in adult patients with chronic cough: A systematic review and meta-analysis

Cough is an important reflex we need to remove irritants from the airways, but for many people, a hypersensitive cough reflex can negatively affect quality of life.  A major trigger of chronic cough is airway inflammation from immune cells including type 2 helper T-cells (TH2), but conventional tests required for diagnosis are technically challenging and often require specialist expertise.  Fortunately, measurement of the fractional exhaled nitric oxide (FENO), a potential marker of TH2 airway inflammation, has become much more common in allergy and pulmonary practices.  In this month’s issue of JACI, Song and colleagues review the literature on the use of FENO to diagnose Cough-Variant Asthma (CVA) and Eosinophilic Bronchitis (EB), two major causes of TH2-mediated chronic cough (J Allergy Clin Immunol 2017; 140(3): 701-709).

They looked at thousands of articles from multiple databases in order to answer the question “What is the diagnostic accuracy of FENO for CVA and/or EB in patients with chronic cough?”   After an exhaustive search, they found 15 studies with 2187 adult patients.  The authors then collected and compared the data to determine the accuracy.  Overall, when looking at either CVA or EB, the pooled sensitivity and specificity were 0.73 and 0.89.  For diagnosing CVA, they found moderate diagnostic accuracy, suggesting that the FENO test alone is not sufficient to diagnose CVA.  However, its high specificity means that it may be more useful as a rule-in test than as a rule-out test.  In contrast, results for EB suggested that FENO testing may not be precise enough for prediction. 

This article provides guidance on how to further research on how best to use FENO testing in patients with chronic cough. However, there remain many unanswered questions because of limitations of the review, including the limited number of studies, generalizability of studies which were mostly conducted in Asia, and the imprecision of current diagnostic criteria for CVA.  

Comments

Post a Comment

Popular posts from this blog

Features of the bronchial bacterial microbiome associated with atopy, asthma and responsiveness to inhaled corticosteroid treatment

It’s been known that asthmatic lungs are different from healthy lungs in many aspects, including housing different strains of bacteria.  So far, studies haven’t been able to tell whether these differences are due to asthma, associated allergies (atopy), or treatment with different drugs.  They also haven’t been able to determine how these differences affect the way asthma manifests itself and how asthma can be treated.  In this month’s issue of JACI, Durack and colleagues aim to answer these pressing questions ( J Allergy Clin Immunol 2017; 140(1): 63-75 ). Durack and other investigators looked at the bacterial communities in 84 individuals, split into three groups: (1) 42 atopic asthmatic subjects, (2) 21 atopic non-asthmatic subjects, and (3) 21 non-atopic non-asthmatic, otherwise healthy, subjects.  They also looked at inflammatory markers and changes in bronchial hyperresponsiveness after 6 weeks of treatment with fluticasone, an inhaled steroid commonly used for...
Read more

Introducing an environmental assessment and intervention program in inner-city schools

Few studies have comprehensively examined the role the school environment plays in asthma and how effectively changing the environment may reduce morbidity, when adjusting for exposures in the home. In their review, Huffaker and Phipatanakul summarize the importance and common challenges of school-based environmental assessment and intervention studies linked to health effects ( J Allergy Clin Immunol 2014; 134: 1232-1237 ). They discuss the challenges and potential benefits of comprehensive environmental assessment and health outcomes in inner-city schools. The school environment has been shown to be a significant reservoir for allergens and pollutants. Indoor allergens known to be important in urban home environments may also be important in schools, including cockroach, cat, dog, mouse, dust-mite, and molds. Studies have identified children with asthma in inner-cities have markedly higher levels of mouse allergen in their schools compared to levels in their individual bedrooms. Give...
Read more

Role of viral infections in the development and exacerbation of asthma in children

Wheezing is a common complaint among parents of infants.  About 1 in 5 children have acute wheezing illnesses in their first two years of life.  This is important because an overwhelming majority of these wheezing illnesses are related to viruses, and are linked to asthma development.  In this month’s issue of JACI, Jartti and Gern review the role of viral infections in the development of asthma in children ( J Allergy Clin Immunol 2017; 140(4): 895-906 ).  They survey the viruses -rhinoviruses, respiratory syncytial viruses, and others – and how they impact the developing set of lungs.  Genetic variation and low interferon responses are two factors that increase the risk of these types of infections.  In addition, increased eosinophil counts in blood and nasal mucus and atopic eczema all increase the risk of later asthma.  Additionally, viral infections can lead to exacerbations in children who already have asthma.  This may explain why the rates...
Read more