LAUSR

Clear definitions of “difficult asthma” and “severe asthma” are very important in terms of using a common language in our daily practice. If a patient is diagnosed with severe asthma, determination of phenotypic patterns and assessing targeted treatments according to these phenotypes should be the next step. However, physicians often use the terms “severe asthma” and “difficult asthma” interchangeably and disagreeably. The term “difficult asthma” (also known as difficult-totreat asthma or difficult-to-control asthma) is used for patients whose condition is uncontrolled despite GINA step 4 or 5 treatment. This uncontrolled asthma may be difficult to treat owing to inadequate or inappropriate treatment, comorbidities such as obesity, gastroesophageal reflux disease, chronic rhinosinusitis, poor adherence, and allergen exposure. Asthma may also be misdiagnosed. It is recommended that patients presenting with “difficult asthma” have their asthma diagnosis confirmed and be evaluated and managed by an asthma specialist for longer than three months [1]. The most commonly accepted terminology for “severe asthma” (also known as refractory severe asthma, therapy-resistant asthma, or difficult-to-treat asthma), defined by the Task Force and supported by the European Respiratory Society and American Thoracic Society is, “The disease that remains uncontrolled despite GINA step 4 or 5 treatment (high dose ICS and LABA or leukotriene modifier/theophylline) for the previous year, or treatment with systemic corticosteroids for at least half of the past year, or if the disease can only be controlled with these treatments.” [1]. In other words, “severe asthma” is a subset of “difficult asthma”. The most significant point in these terminologies is that all difficult asthma should not need to be severe asthma. Difficult asthma can be defined as severe asthma only if all the factors have been excluded (Figure 1). GINA’s definition of severe asthma is the same as the ATS/ERS consensus definition of severe asthma, and it has been reported that the definition of severe asthma should only be reserved for patients with truly severe asthma (refractory severe asthma or therapy-resistant asthma) [2].