Usefulness of induced sputum in investigating occupational asthma with normal responsiveness to methacholine: a case report

Airway Hyperresponsiveness in Asthma: Measurement and Clinical Relevance

Airway hyperresponsiveness is a characteristic feature of asthma, and its measurement is an important tool in its diagnosis. With a few caveats, methacholine bronchial provocation by a 2-minute tidal breathing method is highly sensitive; a negative test result (PC₂₀ > 16 mg/mL, PD₂₀ > 400 μg) rules out current asthma with reasonable certainty. A PC₂₀ value of less than 1 mg/mL/PD₂₀ value of less than 25 μg is highly specific (ie, diagnostic) but quite insensitive for asthma. For accurate interpretation of the test results, it is important to control and standardize technical factors that have an impact on nebulizer performance. In addition to its utility to relate symptoms such as cough, wheeze, and shortness of breath to variable airflow obstruction (ie, to diagnose current asthma), the test is useful to make a number of other clinical assessments. These include (1) evaluation of patients with occupational asthma, (2) evaluation of patients with exercise-induced respiratory symptoms, (3) evaluation of novel asthma medications, (4) evaluation of relative potency of inhaled bronchodilators, (5) as a biomarker to adjust anti-inflammatory therapy to improve clinical outcomes, and (6) in the evaluation of patients with severe asthma to rule out masqueraders such as laryngeal dysfunction. The actual mechanism of altered smooth muscle behavior in asthma that is assessed by direct (eg, methacholine) or indirect (eg, allergen) bronchial provocation remains one of the most fundamental questions related to asthma that needs to be determined. The test is underutilized in clinical practice.

Advanced diagnostic studies: exhaled breath and sputum analyses

AIM

: The present paper aims to review the advantages and limitations of sputum cell counts and exhaled nitric oxide (FeNO) levels in the investigation of occupational asthma (OA).

METHODS

The American College of Chest physicians held a course on occupational and Environmental Lung Diseases in Toronto in 2013. A summary of the session on non-invasive measures of airway inflammation in OA is presented here.

RESULTS

Occupational asthma is associated with an increase in sputum eosinophil percentage during periods at work or after positive specific inhalation challenges. Changes in FeNO are less sensitive than sputum eosinophil counts for predicting OA.

CONCLUSIONS

In settings where this tool is available, sputum eosinophil counts may complement the current investigation of OA. The interpretation of FeNO remains sometimes difficult. The phenotypes of patients who may benefit from this measure needs to be better defined.

High eosinophil levels and poor evolution in occupational asthma due to cyanoacrylate exposure

We present the case of a 41-year-old woman who developed occupational asthma (OA) due to cyanoacrylate while working in a company that manufactured and marketed plastic products. Specific inhalation challenge confirmed the diagnosis of OA to cyanoacrylate. The patient expressed marked eosinophilic inflammation and marked deterioration of pulmonary function while in persistent contact with the causal agent. The possible etiologic mechanisms implicated in the origin of this type of OA are discussed. Patients diagnosed with this condition are advised to avoid exposure to cyanoacrylates.

Noninvasive methods for assessment of airway inflammation in occupational settings

The present document is a consensus statement reached by a panel of experts on noninvasive methods for assessment of airway inflammation in the investigation of occupational respiratory diseases, such as occupational rhinitis, occupational asthma, and nonasthmatic eosinophilic bronchitis. Both the upper and the lower airway inflammation have been reviewed and appraised reinforcing the concept of 'united airway disease' in the occupational settings. The most widely used noninvasive methods to assess bronchial inflammation are covered: induced sputum, fractional exhaled nitric oxide (FeNO) concentration, and exhaled breath condensate. Nasal inflammation may be assessed by noninvasive approaches such as nasal cytology and nasal lavage, which provide information on different aspects of inflammatory processes (cellular vs mediators). Key messages and suggestions on the use of noninvasive methods for assessment of airway inflammation in the investigation and diagnosis of occupational airway diseases are issued.

Advances in environmental and occupational disorders in 2008

Substantial progress in understanding the role of environmental factors in allergic disease and asthma has been made in the past year. A number of new allergens have been described, and the impact of exposure to indoor allergens in the development of allergic respiratory disease is further confirmed. Exposures to environmental pollutants, particularly tobacco smoke in children, have furthered our knowledge of the detrimental effects of these exposures. This review highlights key advances in environmental and occupational exposures that contribute to the burden of allergic respiratory disease.