Measuring outcomes in PAH: the gap between the measures that are used and their validity

Pulmonary arterial hypertension (PAH) has poor prognosis in systemic sclerosis (SSc), and at present the "gold standard" for diagnosis and follow-up of PAH in SSc is right heart catheterization (RHC) but it would be very useful to have a noninvasive way to follow these patients. Using the OMERACT criteria for validation of measures of response, the only fully validated measure for PAH in SSc has been the 6-min walking test. Multiple other measures are particularly valid (e.g., echocardiography, brain natriuretic protein [BNP], FV/DLCO) while a few are unlikely ever to be validated for various reasons (e.g., symptoms, MRA). A Delphi exercise among 78 experts (EPOSS) has been done and has developed a consensus document consisting of eight domains (lung vascular/PAP, exercise capacity, cardiac function, dyspnea, discontinuation of treatment, quality of life, lung parenchymal, and global state), which can be used and must be tested.