In medicine, the importance of terminology is not sufficiently discussed, despite the fact that diagnoses and the terms used to name them have such an important role.  Scientific medicine aims to establish a concept based on the aetiology or at least the pathogenesis of a disease. Unfortunately, in my opinion, this aim is often missed.To give an example: I question the meaningfulness or quality of the diagnostic term chronic obstructive pulmonary disease (COPD), and I wonder whether the diagnosis of COPD possibly represents an obstacle to progress in identifying the pathogenesis and therapy of bronchial diseases. COPD is an undifferentiated catch-all—a description, rather than a proper diagnosis which stops doctors looking at the root causes.
Scientifically based medical terminology promotes our understanding of the disease process.  So called diagnoses that merely name symptoms—such as back pain, or headache—do not reveal the cause of the disorder underlying the symptom. They are merely operational and useful for therapeutic purposes. However, in practice, such operational diagnoses are of limited usefulness if they are to be used as the basis for a scientific understanding of the disease process.
The problem of diagnoses that provide a functional description of a condition is particularly evident in the diagnosis of COPD, in which the dysfunction—the “obstruction”—is the defining parameter. However, the terminology/diagnosis “COPD” is used inconsistently. It is generally used to describe all obstructive diseases of the lungs. Asthma is explicitly excluded by the term COPD, whereas other conditions whose differences are greater than their similarities—such as bronchitis and emphysema—are subsumed under one label. The diagnosis COPD does not include bronchial diseases without obstruction.  The use of the term restricts any aetiological or pathogenic perspective and hampers any deeper insight into our understanding of the subject. The term COPD is based on a symptom—obstruction—but it does not contain any information about pathogenesis or prognosis of the disease.
Until well into the 1980s, any inflammatory disease of the bronchial system was diagnosed as bronchitis, which in my view is the correct term. Without doubt, COPD is a disease, but the term provides no more information than a mere description of symptoms. It completely disguises the extraordinary variety of diseases of the bronchial and pulmonary tissues. And yet this poorly defined term conquered the medical world very rapidly: the catch-all COPD became widely accepted, particularly in the US, where it culminated in the so called GOLD initiative (www.goldcopd.org).  Nevertheless, the fact that the term COPD became essential for developing of successful treatments is indisputable. 
For some, the therapeutically focused concept of COPD has lost its relevance in recent years.  It is too simple to encompass the diversity of the development and progression of bronchial diseases. Attempts to characterise different phenotypes have failed because the result of the disease, the obstruction, has dominated the terminology and the discussion around it. The scientific helplessness expressed by the term COPD is clearly illustrated by the new “disease” of asthma-COPD overlap syndrome.  Critically, the term COPD does not allow for any possibility to differentiate between diseases as its focus is on the dysfunction itself.
In the past, the dysfunction was regarded as a symptom of a bronchial disease, not as its defining criterion.  An obstruction is a common, but by no means constituent, symptom of a bronchial inflammation. Moreover, inflammation can vary greatly in its extent, and some inflammations affecting the bronchial system are undoubtedly not associated with obstruction—for example, those triggered by viral infections, systemic or related diseases, or the effects of tobacco smoking.  These conditions are not covered by the diagnosis COPD , and neither are patients with respiratory symptoms, but whose lung function is normal. 
We need to characterise patients with bronchial diseases in as much detail as possible, using all the methods available.  “Bronchitis” would be a better term to describe the causality of bronchial diseases. This simple terminology could easily be supplemented with additional information regarding different aetiology or pathogenesis. This would allow a much broader view of bronchial diseases than the current diagnostic concept of COPD.
Peter von Wichert, Professor of Medicine, Chairman emer. Dept of Medicine, Philipps University Marburg, Germany
Competing interests: None declared.
1 Scadding, J G, Meaning of diagnostic terms in broncho-pulmonary disease, Brit Med J 1963; 1425 -1430
2 Rodriguez-Roisin R, Han M, Vestbo J, Wedzicha JA, Woodruff PG, Martinez FJ, Chronic respiratory symptoms with normal spirometry, Am J Respir Crit Care Med 2017; 195: 17-22
3 Pauwels RA, Buist S A, Calverley P M, et al. Global strategy for the diagnosis, management and prevention of chronic obstructive pulmonary disease. NIHLBI/WHO global initiative for chronic obstructive Lung Disease ( GOLD ) Workshop summary, Am J Respir Crit Care Med 2001;163: 1256-1276
4 Rabe, KF, Hurd S, Anzueto A, Barnes PJ, Calverley P, Fukuchi Y, Jenkins C, Rodriguez-Roisin R, van Weel C Zielinski J, Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: GOLD executive summary, Am J Respir Crit Care Med 2007; 176: 532-555
5 Gibson PG, McDonald VM, Asthma-COPD overlap 2015, Thorax 2015; 70: 683-691
6 Stuart-Harris CH, Chronic Bronchitis, Abstr. World Med 1968; 42: 649-751
7 Woodruff PG, Barr RG, Bleeker E, Christenson SA et al. Clinical significance of symptoms in smokers with preserved pulmonary function, New Engl. J Med 2016; 374: 1811 – 1821
8 Han MK, Agusti A, Calverley, PM et al, Chronic obstructive pulmonary phenotypes: The future of COPD, Am J Respir Crit Care Med 2010; 182: 598-604
9 Postma DS, Rabe KF, The Asthma-COPD overlap syndrome, New Engl J Med 2015; 373: 1241-1249