Measuring Outcomes in PAH: The Gap between the Measures That Are Used and Their Validity

Outcome measures in rheumatologic clinical trials and systemic sclerosis

OMERACT (Outcome Measures in Rheumatologic Clinical Trials) is a loose organization of rheumatologists, epidemiologists and statisticians whose aim is to improve measurements in the rheumatic diseases. In this context, some SSc measures of response have been found to be valid: the modified Rodnan skin score, the Raynaud's condition score, the forced vital capacity as part of pulmonary function tests, right heart catheterization haemodynamics, serum creatinine, blood pressure and complete blood counts in scleroderma renal crisis and serum creatine phosphokinase as a measure of muscle disease in SSc. Other measures are being tested and have nearly been validated, including the gastrointestinal questionnaire in SSc. Finally, some measures have been found wanting or are not fully tested--in this case for pulmonary arterial hypertension, where effort is presently being focused. These include the echocardiogram, high-resolution CT scan of the lungs, pulmonary function tests, 6-min walking test and MRI.