Fractional Exhaled Nitric Oxide (FeNO) in the Screening and Diagnosis Work-Up of Occupational Asthma

Asthma Phenotypes and Host Risk Factors Associated With Various Asthma-Related Outcomes in Health Workers

Background: Work-related asthma phenotypes in health workers (HWs) exposed to cleaning agents have not been investigated extensively as other occupational exposures. This study aimed to describe asthma phenotypes and to identify important host risk factors associated with various asthma-related outcomes.

Methods: A cross-sectional study of 699 HWs was conducted in two large tertiary hospitals. A total of 697 HWs completed questionnaire interviews. Sera collected from 682 HWs were analyzed for atopy (Phadiatop) and IgE to occupational allergens (NRL—Hev b5, Hev b6.02; chlorhexidine and ortho-phthalaldehyde—OPA). Methacholine (MCT), bronchodilator challenge (BDR) and fractional exhaled nitric oxide (FeNO) were performed. An asthma symptom score (ASS) used five asthma-related symptoms reported in the past 12 months. Current asthma was based on use of asthma medication or an asthma attack or being woken up by an attack of shortness of breath in the past 12 months. Nonspecific bronchial hyperresponsiveness (NSBH) was defined as having either a positive MCT or a significant bronchodilator response. Two continuous indices of NSBH [continuous index of responsiveness (CIR) and dose-response slope (DRS)] were calculated.

Results: The prevalence of current asthma was 10%, atopic asthma (6%) and non-atopic asthma (4%). Overall, 2% of subjects had work-related asthma. There was a weak positive association between NSBH and FeNO [CIR: Beta coefficient (β) = 0.12; CI: 0.03–0.22 and DRS: β = 0.07; CI: 0.03–0.12]. Combining FeNO ≥ 50 ppb with a BDR [mean ratio (MR) = 5.89; CI: 1.02–34.14] or with NSBH (MR = 4.62; CI: 1.16–18.46) correlated better with ASS than FeNO alone (MR = 2.23; CI: 1.30–3.85). HWs with current asthma were twice as likely to be atopic. FeNO was positively associated with atopy (OR = 3.19; CI: 1.59–6.39) but negatively associated with smoking status (GMR = 0.76; CI: 0.62–0.94). Most HWs sensitized to occupational allergens were atopic.

Conclusion: Atopic asthma was more prevalent than non-atopic asthma in HWs. Most asthma-related outcomes were positively associated with allergic predictors suggesting a dominant role for IgE mechanisms for work-related symptoms and asthma associated with sensitization to OPA or chlorhexidine.

Prevention of baker's asthma

PURPOSE OF REVIEW

Baker's allergy and asthma continue to represent an important contributor of occupational asthma globally. This review identified recent studies related to the prevention of baker's allergy and asthma.

RECENT FINDINGS

Studies with respect to regulatory exposure standards, workplace control measures aimed at reduction of flour dust exposures, surveillance programmes (exposure monitoring, medical surveillance) and workplace information, education and training programmes were identified.

SUMMARY

Detailed knowledge on risk factors and detection methods to assess exposure and early identification of high-risk workers exist, but workplace control measures remain sub-optimal because they are rarely multifaceted. This is compounded by the lack of health-based exposure standards globally. Exposure level monitoring and medical surveillance are integral to assessing effectiveness of preventive strategies. Triage systems for optimizing the efficiency of medical surveillance programmes show promise, but need replication in different contexts. Future studies need to focus on evaluating the relevance and quantification of peak exposures in increasing risk; developing standardized respiratory questionnaires for medical surveillance; and further exploration of serial fractional exhaled nitric oxide (FeNO) measurements as an adjunct to allergic sensitization for the early identification of baker's asthma and assessing the long-term impact of interventions.

Occupational asthma: clinical phenotypes, biomarkers, and management

PURPOSE OF REVIEW

This review focuses on new findings in the clinical and inflammatory aspects that can help to better identify the different phenotypes of work-related asthma and the development of specific biomarkers useful in diagnosis and follow-up.

RECENT FINDINGS

Studies on phenotyping of occupational asthma, a subtype of work-related asthma, have mainly compared the clinical, physiological, and inflammatory patterns associated with the type of agent causing occupational asthma, namely, high-molecular-weight and low-molecular-weight agents. Most of this research has found that patients with occupational asthma due to high-molecular-weight agents have an associated presence of rhinitis, conjunctivitis, atopy, and a pattern of early asthmatic reactions during specific inhalation challenge. The inflammatory profile (blood eosinophils, sputum cell count, or exhaled nitric oxide) may be similar when occupational asthma is caused by either type of agent. In some studies, severity of asthma and exacerbations have been associated with exposure to low-molecular-weight agents. The most reliable biomarkers in diagnosis and follow-up are eosinophilia in induced sputum and exhaled nitric oxide.

SUMMARY

There are several phenotypes, characterized by its pathogenesis and inflammatory profile. Avoidance of the causative agents does not warrant complete recovery of occupational asthma. Treatment with biologic agents may be considered in severe occupational asthma.