Subjective (Patient–Reported) Outcome. Part 4
This study has several other limitations. First, we studied acute asthmatic responses, so it remains unclear whether our findings would apply to chronic asthma or to other conditions. Even with respect to the treatment of acute asthma, it is important that the findings from our study be replicated to assess their reliability and robustness. In addition, we measured outcomes using a single subjective measure and a single objective measure (FEV1). Future research should investigate whether our findings can be generalized to other subjective and objective measures of acute asthma. Finally, we did not assess subjective symptoms before each visit’s intervention; therefore, the severity of subjective symptoms before each treatment remains unclear. Assessing subjective measurements before and after interventions could have yielded other differences. Although it is possible that the degree of physiological deficit in these patients was not sufficient for them to have symptoms at rest, it is increasingly recognized that not all patients with asthma who have deficits in lung function fully appreciate the degree to which their asthma limits airflow until they are given bronchodilators that result in improvement in lung function, symptoms, or both.26-28 In this study, there was a significant improvement in lung function with the genuine bronchodilator (about 20%) that coincided with an improvement in symptoms, whereas treatment with placebo had no effect on measurable biologic factors but was indistinguishable from medication with regard to subjective outcomes.
Our research has important implications both for the treatment of asthma and for clinical-trial design in general. Many patients with asthma have symptoms that remain uncontrolled, and the discrepancy between objective pulmonary function and patients’ self-reports noted in this study suggests that subjective improvement in asthma should be interpreted with caution and that objective outcomes should be more heavily relied on for optimal asthma care. Indeed, although improvement in objective measures of lung function would be expected to correlate with subjective measures, our study suggests that in clinical trials, reliance solely on subjective outcomes may be inherently unreliable, since they may be significantly influenced by placebo effects. However, even though objective physiological measures (e.g., FEV1) are important, other outcomes such as emergency room visits and quality-of-life metrics may be more clinically relevant to patients and physicians. Although placebos remain an essential component of clinical trials to validate objective findings, assessment of the course of the disease without treatment, if medically appropriate, is essential in the evaluation of patient-reported outcomes.