The 6MWT as a prognostic tool in pulmonary arterial hypertension: results from the COMPERA registry

Background In patients with pulmonary arterial hypertension, the 6-Minute Walk Test (6MWT) is recommended for risk stratification and follow-up by all guidelines. However, the prognostic value of the 6MWT has been discussed controversially. We sought to compare and validate all published 6MWT cut-off points. Methods From the Comparative, Prospective Registry of Newly Initiated Therapies for Pulmonary Hypertension (COMPERA)-registry we identified 2391 patients with pulmonary arterial hypertension who had at least one documented 6MWT measurement. A Medline search identified a total of 21 different threshold values for either single-point or change of 6MWT. All values were tested individually for prognostication of 1-year, 2-year and 3-year all-cause mortality. Results The highest positive likelihood ratio was a cut-off value < 165 ms, whereas the best negative likelihood ratio was found to be a threshold of 440 ms. Furthermore, improvement in 6MWT had considerably less predictive value on mortality and survival than deterioration. Moreover, absolute single-point values outperformed change values for both improvement and worsening. Conclusion Our data confirmed the prognostic relevance of the 6MWT and support the cut-off values stated in most recent guidelines. Furthermore, these results explain why changes in 6MWT did not correlate consistently with prognosis in previous studies.