Hope for Pulmonary Arterial Hypertension Patients: Minimal Important Difference in 6-Minute-Walk Distance

The 6-minute-walk distance (6MWD) test has been used as an objective measure of physical performance in clinical practice for respiratory patients since the early 1960s. It has become a core measure for risk assessment that guides therapy selection and escalation for patients with pulmonary arterial hypertension (PAH). The minimal clinically important difference (MCID) is the smallest difference in score in the outcome of interest that patients perceive as important, either beneficial or harmful, and that leads to consideration of a change in disease management. In the PAH field, working groups called for trial endpoints that are meaningful for patients, and the MCID was later defined as +33m to +36m in 6MWD based on meta-analysis, which did not differ by age, sex, race, pulmonary hypertension subtype, or background therapy.