Asthma is a complex heterogenous disorder of the airways characterized by chronic airway inflammation associated with airway hyperresponsiveness. This further leads to recurrent episodes of cough, wheeze, breathlessness and chest tightness.Due to multiple overlapping symptoms of other syndromes of the airways, the identification of the asthma phenotypes is a major challenge in the management of the disorder. A number of invasive and non-invasive techniques are available for the diagnosis, assessment and treatment of severe asthma. Non-invasive methods for assessing the disease phenotype include: Fraction of Exhaled Nitric Oxide (FeNO), Induced sputum, High Resolution Computed Tomography (HRCT) and Asthma Control Test (ACT). Electronic nose (e-nose) and Exhaled breath condensate may also prove beneficial in monitoring the disease phenotype in severe asthma. Invasive techniques for severe asthma include: Fiberoptic Bronchoscopy with Bronchoalveolar lavage (BAL) and Bronchial biopsy.
a) Fraction of Exhaled Nitric Oxide (FeNO):Increased FeNO indicates eosinophillic inflammation and predicts responsiveness to steroids in patients with multiple symptoms.. Decrease in FeNO is associated with the use of inhaled corticosteroids.
b) Induced sputum: Used for differential cell count: Eosinophils and Neutrophils. So, used to assess eosinophilic inflammation (allergic) and neutrophilia (non-allergic).
c) High Resolution Computed Tomography (HRCT):Helps in investigating the structural lung changes such as airway remodeling, bronchial wall thickening,bronchiectasis.
d) Asthma Control Test (ACT): This is a questionnaire based approach proposed by GINA,2006. This involves the improvement of the evaluation of asthma control and management of asthmaphenotypes by promoting the communication between patients and health care professionls.
e) Electronic nose (e-nose): It recognizes the pattern of exhaled volatile organic compounds using a biological sensor yielding a smell print. However, it is under investigation and has not been used in severe asthma.
f) Exhaled breath condensate: Acidification of exhaled breath (low pH) and other biomarkers indicates severe/uncontrolled asthma.
a) Fiberoptic Bronchoscopy: Bronchoalveolar Lavage obtained from bronchoscopy helps in examination of airway remodelling, cytokine profile and eosinophilia. Bronchoscopy plays an important role in phenotyping asthma in patients with non-specific symptoms.
b) Bronchial biopsy: Bronchoscopy with biopsy is performed to obtain tissue from the lining of bronchi and alveoli. The tissue is further analyzed to see the abnormalities such as: tumors, infections (fungal and bacterial), pneumonitis, vasculitis and granulomas. Presence or absence of these abnormalities help in defining the phenotype of asthma.