Researchers determined that the minimal clinically important difference in 6-minute walk distance (6MWD) is around 33 meters for adults with pulmonary arterial hypertension (PAH). Their study is published in the American Journal of Respiratory and Critical Care Medicine.

PAH is characterized by elevated pulmonary vascular resistance and right ventricular failure. Clinical trials that have led to the regulatory approval of drugs have used the 6MWD as the primary outcome measure. 

Generally, a decrease of more than 15% from baseline is considered clinically significant, although there is no strict consensus on this. It is thought that identifying the minimal clinically important difference in 6MWD may allow for objective comparison between various interventions. 

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“The minimal clinically important difference is the smallest change in an outcome measure that a patient would identify as meaningful and which would mandate a change in the patient’s management, in the absence of significant side effects or excessive cost,” the authors of the study wrote. 

Read more about PAH etiology

The research team hence sought to determine the minimal clinically important difference for 6MWD using data from PAH clinical trials. They obtained the results of 8 randomized clinical trials submitted to the US Food and Drug Administration (FDA) that used the 6MWD as an outcome measure. The researchers then anchored their estimates of the minimal clinically important difference in 6MWD using the Pulmonary Hypertension Association Registry. 

From these 8 studies, the researchers identified 2404 adult patients with PAH and relevant clinical data. They determined the minimal clinically important difference to be approximately 33 meters using the anchor-based approaches described. 

The establishment of the minimal clinically important difference in 6MWD could significantly streamline future clinical trials and offer regulatory bodies a further technique for weighing the benefits of any new interventions. Clinicians in turn can use this to define treatment goals and monitor disease evolution in their patients.


Moutchia J, McClelland RL, Al-Naamani N, et al. Minimal clinically important difference in the six-minute walk distance for patients with pulmonary arterial hypertensionAm J Respir Crit Care Med. Published online January 11, 2023. doi:10.1164/rccm.202208-1547OC