With the availability of numerous PROs, it is important to understand which provide a better evaluation of patients' health status and demonstrate responses to treatment. Even when PROs evaluate the same parameter, e.g. dyspnoea, they may not always capture a uniform response. Hence, it would be useful to examine if the PROs correlate with each other and whether any specific PROs better reflect treatment benefit (as expressed by minimal clinically important differences (MCIDs)) than the others. Furthermore, understanding the relationship between the PROs and lung function (FEV1) may provide insights into whether a change in lung function translates to a change perceptible by the patients (assessed through PROs).
Tiotropium is a potent, long-acting, selective anticholinergic bronchodilator. Treatment with tiotropium produces sustained improvements in lung function, particularly FEV1 (peak, trough, average, and area under the curve) compared with either placebo or ipratropium in patients with moderate to severe COPD. Preliminary evidence suggests that treatment with tiotropium may slow the rate of decline in FEV1, but this finding awaits confirmation. Tiotropium reduces lung hyperinflation, with associated improvements in exercise capacity. Tiotropium, compared with either placebo or ipratropium, improves a variety of patient-centered outcomes, including subjective dyspnea ratings and Health Related Quality of Life (HRQL) scores. Tiotropium reduces the frequency of COPD exacerbations and of hospitalizations due to exacerbations, but has not been shown to reduce all-cause mortality. Compared with the long-acting bronchodilators, tiotropium provides incrementally better bronchodilation, but it is not clearly superior in terms of patient-centered outcomes. Tiotropium has a good safety profile; however patients with severe cardiac disease, bladder outlet obstruction, or narrow angle glaucoma were excluded from all studies.
