Chronic obstructive pulmonary disease (COPD) is a very frequent disease in the Spanish population. In this country the disease is estimated to affect 9% of all persons older than 40 years, and 20% of all persons older than 65 years. Moreover, because of its close etiological association with smoking, these figures are expected to rise. Nonetheless, the importance of this disease does not lie in its elevated prevalence alone; other factors that must be taken into account are its high economic costs, consumption of resources, occupational repercussions, associated morbidity and mortality, and the severe decline in quality of life in these patients. Together, these factors make COPD a social and health problem of the first order.
Several interesting projects have recently been carried out to raise awareness of this disease. One such initiative, under the auspices of an international committee of experts, has arisen within the World Health Organization (WHO) and the US National Institutes of Health (NIH). The GOLD project (Global Initiative for Chronic Obstructive Lung Disease) is a world-wide consensus on strategies for the diagnosis, management and prevention of COPD1. Another initiative, undertaken in Spain, is the Joint Document of the Spanish Society of Family and Community Medicine (semFYC) and the Spanish Society of Pneumology and Thoracic Surgery (SEPAR) regarding recommendations for the care of patients with COPD2. This document aims to serve as a guide to both primary care physicians and pneumologists for the daily management of this disease, and places particular emphasis on the importance of collaboration between both specialists to achieve the best possible use of available resources.
Despite these efforts, we are facing a chronic, incapacitating disease for which there is currently no curative treatment, and which has considerable psychological and social effects. These characteristics are inadequately evaluated with objective clinical and functional methods, whose results do not correlate well with self-perceived health or with subjective improvements seen after certain treatments and rehabilitation programs. For these reasons quality of life studies have been added, in recent years, to the management of COPD4.
Health-related quality of life (HRQL) is a concept that comprises the evaluation and interpretation by patients of the repercussions of their illness on their person and their life style. This evaluation is conditioned by different factors such as beliefs, education, occupation, and life experience with the illness. The patient's vision of the illness often fails to match the view that might be deduced from clinical and functional data. In such a situation, we should ask how patients ought to be evaluated, and whether the health of someone with COPD can actually be "measured."
This interesting issue is dealt with in an extraordinary study published in this issue of Atención Primaria. The authors set out to study how an objective measure of health such as spirometry is related with a subjective measure of HRQL. The questions raised by this study are of interest in view of the fact that the debate over treatment goals for this disease has shifted substantially with the inclusion of HRQL considerations. For a chronic disease with limited options for intervention, assessment of the impact of symptoms on daily life offers a more global vision of the disease, and can facilitate the choice of the most appropriate treatment for each patient.
Health-related quality of life is measured with questionnaires that explore different aspects of daily life such as severity or intensity of the symptoms, functional involvement and perceived wellbeing5. Such tests are useful, basically, to:
evaluate the therapeutic benefits and secondary effects of drugs in clinical assays,
follow the clinical course of the disease, and
evaluate the patient's overall functional capacity.
Two types of quality of life tests are available: generic instruments aimed at exploring a wide spectrum of health problems (for example, the Sickness Impact Profile and the Nottingham Health Profile), and specific instruments designed to investigate specific aspects, diseases or populations (for example, the Chronic Respiratory Disease Questionnaire and the St. George's Respiratory Questionnaire, both for COPD). All questionnaires have been analyzed in depth to determine their consistency, validity, sensitivity, ease of interpretation, and sensitivity to change. It has been shown that dyspnea, tolerance of exercise, and psychological and emotional aspects related with COPD correlate better with quality of life than with any functional parameter (such as FEV1 or gasometry). As a result, respiratory rehabilitation has regained some importance, as it has been shown to be effective in improving quality of life6.
However, questionnaires also have some limitations. For example, when subjective characteristics are studied the external criteria against which the results are to be compared are unclear. Specific tests correlate well with disease severity, but generic tests do not. Moreover, interpretation of the results is not straightforward. It has been suggested that the joint use of a generic and a specific test may offer a more complete vision. Within this complex framework, the article by Fernández Vargas and colleagues represents a useful way forward in this line of research: to shed light on the field, these authors studied the correlation between a generic and a specific questionnaire. Their results, along with the considerations discussed above, lead to the conclusion that although objective measurements of pulmonary function are fundamental, measuring quality of life is becoming increasingly important. Both types of measures have their drawbacks. The objectivity of spirometry turns into arbitrariness with regard to the choice of cut-off points for obstruction, normal values, or different degrees of severity. On the other hand, the subjectivity that characterizes quality of life assessments becomes imbued with good sense when these instruments are shown to be capable of detecting changes after certain interventions. It is clear that both approaches should be combined to provide a more accurate vision of the complex features of a chronic disease that affects, to a greater or lesser degree, many aspects of the patient's life. Measurements of quality of life provide good estimates of the disease stage or of an individually important and quantifiable aspect of the disease. Hence studies based on quality of life measures--such as the one that appears in this issue--can contribute to the appropriate implementation of suitable therapeutic measures.
