The importance of primary care research in the management of respiratory disease.

1 PRIMARY CARE RESPIRATORY JOURNAL www.thepcrj. org Diseases involving the respiratory tract affect all age groups. They are not only very common but they carry high morbidity and in some cases death, thus leading to high health care utilisation. The great difficulty with these diseases is that appreciable lung pathology can occur before symptoms become apparent or before patients are sufficiently aware of their significance – good examples being lung cancer and COPD, where delayed diagnosis has disastrous consequences. Unlike other organs the lung has few pain receptors except in the pleurae and oropharynx; symptoms manifest as cough, sputum production and shortness of breath. Lung disease has strong links to tobacco smoking, air pollution, industrial exposure and socioeconomic deprivation. Therefore, unlike diseases afflicting other organs such as the heart, endocrine system and central nervous system, respiratory disease has not attracted the attention it deserves. Such neglect has been strengthened by the stigmata that not infrequently accompany smoking-related lung disease or asthma. These complex perceptions operate in most countries and have contributed to the relatively poor progress made in preventing or curing respiratory diseases. However, the World Health Organization (WHO) now recognises that within a few years lung disease, and in particular COPD, will be the third most common cause of death worldwide by 2020, much of it tobacco-related or caused by infection. The recent viral pandemics involving coronovirus causing SARS, and the influenza H5N1 (avian) and H1N1 (swine) outbreaks, illustrate how potentially devastating mutations in microorganisms with which we are familiar – coronovirus usually causes common colds – can be. The acquisition of anti-microbial resistance is an added problem in viral pandemics, nosocomial and community acquired pneumonia, and tuberculosis. Diseases of the upper respiratory tract are also underestimated in their impact, especially rhinitis and rhinosinusitis. Such disorders are often trivialised without us realising their impact on performance and quality of life. Most upper respiratory diseases also coexist with lung disease (especially asthma and COPD) and yet these are rarely considered together when clinical presentation occurs through either the lower or upper respiratory tracts. Finally, there are the less common respiratory diseases that can masquerade as other diseases such as asthma in the beginning, but which turn out to be sleep apnoea, vocal cord dysfunction, autoimmune and eosinophilic lung disease, sarcoidosis, interstitial pulmonary fibrosis or idiopathic pulmonary hypertension. Another important facet of most lung disorders is the heterogeneity that exists in response to individual treatments. The drive towards evidenced-based practice has led to a proliferation of management guidelines with little involvement of those expected to deliver the guideline recommendations. The majority of guidelines rely on randomised control trials to provide the necessary evidence, but these are often conducted in highly selected patient populations that are far from representative of those expected to receive the specific treatment. One example of this is asthma, where less than 4% of the total eligible asthma disease population is eventually included in trials of asthma drugs. These trials then assume that all patients will respond in a similar manner. However, this is simply not true. A good example is the failure of inhaled corticosteroid (ICS) treatment in patients with asthma who smoke, whereas leukotriene receptor antagonists (LTRAs) maintain their efficacy. Put simply, within complex lung disease there are multiple phenotypes involving different causal pathways. The concept of the responder and nonresponder to a therapy is now well accepted even when attention is being paid to treatment adherence. As a speciality, medicine is now moving towards a stratified approach using pathway-specific diagnostic tests to select the most appropriate treatment tailored to a patient’s need. Cancer diagnostics are leading the field, but treatments for chronic inflammatory diseases are close behind. Aside from the pathophysiological reasons for explaining treatment variation, adherence to prescribed treatment is a crucial factor. This is especially so with inhaled drugs which are used to control diseases such as asthma and rhinitis, despite every attempt by health practitioners and pharmacists to teach patients good practice and explain to them the importance of continuing therapy even though they may be free of current symptoms. Guidelines widely state that ICS are superior to LTRAs in the first line treatment of adult asthma, but a recent pragmatic “real world” trial in primary care using patient-related outcome measures as well as lung function failed to The importance of primary care research in the management of respiratory disease