Diagnosis
Spirometry is required for the appropriate diagnosis of obstructive lung disease and should be performed at least annually for assessment of control and disease progression. 5,31,32 Postbronchodilator spirometry is necessary to determine whether obstruction (ie, FEV1/FVC < 0.7), if present, is reversible. 32 In asthma, airway obstruction following bronchodilator administration is typically fully reversible. 5 In COPD, patients will remain obstructed following postbronchodilator administration regardless of the FEV 1 response. 32 In ACOS, the postbronchodilator FEV 1/FVC typically remains obstructed. 5 A normal postbronchodilator FEV 1/FVC is not compatible with the diagnosis of ACOS unless there is other evidence of chronic airflow limitation. 5 Although spirometry confirms the presence of chronic airflow obstruction, it is of limited value in distinguishing between asthma with fixed airflow obstruction, COPD, and ACOS. 5 At times, specialized investigations, such as carbon monoxide diffusion capacity on pulmonary function testing and chest imaging, may also be used to help distinguish between asthma and COPD. 5,31,32
Treatment
Although much has been published on the recognition and identification of ACOS, there is a paucity of information on the effectiveness of therapeutics for this population. Patients with ACOS are frequently excluded from clinical studies involving asthma and COPD, which limits the generalization of findings from these trials to these patients. Although a comprehensive review of the available treatments for obstructive airway disease is beyond the scope of this article, some management tenets will be discussed.
In general, inhaled corticosteroids (ICS) are the cornerstone of the pharmacologic management of patients with persistent asthma, whereas inhaled bronchodilators (beta 2-agonists and anticholinergics) are the therapeutic mainstay for patients with COPD. 31,32 In those with ACOS, the default position should be to start treatment with low or moderate dose ICS in recognition of the role of ICS in preventing morbidity and mortality in those with asthma. 5 Depending on severity, a long-acting beta 2-agonist (LABA) could be added or continued if already prescribed for those with ACOS. 5 Patients should not be treated with a LABA without ICS if there are features of asthma. 5
Treatment of ACOS should also include advice about other therapeutic strategies such as smoking cessation, pulmonary rehabilitation, influenza and pneumococcal vaccinations, and treatment of other comorbid conditions. 5 The treatment goals of ACOS are similar to those of asthma and COPD in that they are driven by controlling symptoms, optimizing health status and QOL, and preventing exacerbations. Although there are currently no disease-modifying medications that can alter the progression of airway obstruction in either asthma or COPD, smoking cessation is an essential component of the successful management of all obstructive airway disorders, because it is a modifiable risk factor.
The initial management of asthma and COPD can be carried out at the primary care level. All current guidelines for asthma, COPD, and ACOS provide
recommendations for specialty referral for further diagnostic and therapeutic consideations. 5,31,32 As ACOS is associated with more severe disease and greater health care utilization, specialty referral for this subgroup should be considered.