Objective: To assess the validity of the 6 min walk test (6MWT) in pulmonary arterial hypertension secondary to systemic sclerosis (PAH-SSc) according to the OMERACT filter.
Methods: A systematic literature search was conducted from 1966 through June 2009. The assessment of validation of the 6MWT was based on the OMERACT filter criteria with the domains 'truth', 'discrimination' and 'feasibility'.
Results: From the 57 articles identified, 9 (16%) were analysed. The 6MWT had face validity as it has been accepted by the registration agencies as a surrogate of PAH-SSc. It was sensitive to change in response to therapy, with effect sizes ranging from 0.30 to 1.37 with a parallel variation of haemodynamic parameters measured by right heart catheterisation. Feasibility was also validated. Content validity was not confirmed as this test was not specific for PAH-SSc. There was some evidence that 6MWT might meet criterion/construct validity, reproducibility and sensitivity to change over time, but insufficient data were provided to fully validate these components.
Conclusions: Current evidence suggests partial validation of the 6MWT in PAH-SSc according to the OMERACT filter. Further dedicated studies are needed to validate completely the 6MWT in PAH-SSc, taking into account the comorbidities interfering with the 6MWT.