Measurement of dyspnea and quality of life in advanced lung disease

Abstract

An important aspect of disease management is the ability to measure and report health outcomes. For advanced lung diseases, both dyspnea and HRQOL are key clinical outcomes of interest to patients and health care providers. There are two major reasons to measure those constructs: to differentiate between individuals (or populations) who have varying degrees of the quality (i.e., more dyspnea or better HRQOL); and to evaluate how much dyspnea or HRQOL has changed as a result of a specific intervention or therapy (e.g., LVRS or transplantation). Dyspnea can be measured by clinical instruments-usually questionnaires-that consider various dimensions or components that affect the individual's breathlessness and by direct ratings during a physical task or exercise test. Although multidimensional instruments provide an "indirect" measure of dyspnea, those scales have been tested extensively and have demonstrated significant improvements with a variety of treatments for patients with advanced lung diseases. Another approach is to instruct the patient to rate dyspnea during an exercise test, then examine the full range of dyspnea responses throughout exercise. Disease-specific and generic instruments are available to measure HRQOL. For clinical trials evaluating a new therapy or procedure, disease-specific measures are more appropriate because patients and clinicians find the items more relevant. Furthermore, there is greater potential for demonstrating a significant change with a disease-specific instrument (i.e., it is more responsive). If a clinical outcome of a treatment currently exists, however, then a generic HRQOL instrument may be used to provide complementary information. Such data may expand the impact or scope of the therapy, and previously unrecognized adverse effects may be detected. Another advantage of a generic measure is that comparisons can be made across conditions and populations. Clearly, the selection of the HRQOL instrument depends, in large part, on the objective or question of the clinical trial. An essential consideration for both dyspnea and HRQOL instruments is clinical applicability (i.e., can the questionnaire be used in the daily practice of medicine?). Key factors include the number of items to be completed, the possible need for an interviewer, the time for the patient to complete the instrument, and the ability to computerize scoring and results. Although shorter versions of established "full" instruments are available, the responsiveness and validity of the shorter questionnaires need to be tested by comparing the two versions. Finally, translation of an existing instrument into a new language requires re-examination of the measurement criteria (validity, reliability, and responsiveness). We anticipate a growing interest in measurement of clinical outcomes for patients with advanced lung diseases in the foreseeable future. We expect that current instruments may be modified and that, certainly, new tools will be developed in an attempt to improve the ability to measure dyspnea and HRQOL. Clearly, it is an ongoing process.