Asthma, COPD or overlap? Symptoms and diagnostic procedures Abstract. Medical history combined with spirometry before and after bronchodilation provides important information, and allows distinguishing between asthma and Chronic obstructive pulmonary disease (COPD) in most of the cases. COPD and asthma are sometimes difficult to discriminate, mainly in older patients with a smoking history and /or history of atopia. Symptoms and the results of diagnostic tests are the basis on which therapeutic decisions are made. Differentiation between asthma and COPD is of great importance because management approaches and goals for these conditions differ. Asthma-COPD-overlap has to be considered if a significant interleave of clinical features of both conditions is identified. If it is not possible to differentiate between the two conditions, ways of additional diagnostic testing are described in this article.