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The 6 minute walk test (6MWT) is a clinically relevant and appropriate target for patients with pulmonary arterial hypertension (PAH), according to an analysis of the COMPERA Registry (Comparative, Prospective Registry of Newly Initiated Therapies for Pulmonary Hypertension; ClinicalTrials.gov Identifier: NCT01347216) data published in Clinical Research in Cardiology.
Although the 6MWT is recommended by all guidelines for risk stratification and follow-up in patients with PAH, the prognostic value of the test has been the subject of much debate. The authors sought to compare and validate the predictive value of all previously published 6MWT cutoff points with respect to 1-year, 2-year, and 3-year all-cause mortality in a multicenter real-world population from COMPERA.
A total of 2391 patients with PAH and ≥1 documented 6MWT measurement were eligible for the study. Because no follow-up values were available for 213 patients after the second 6MWT measurement, 2178 individuals qualified for the survival analysis. Median follow-up was 32.4 months; median time between the two 6MWT measurements was 14.0 weeks.
The highest positive likelihood ratio was a cutoff value of <165 ms; conversely, the best negative likelihood ratio was a threshold of >440 ms. Improvement in 6MWT had considerably less predictive value for mortality and survival than for deterioration. In addition, absolute single-point values outperformed change values with respect to improvement and worsening.
In the univariate analysis for 1-year mortality, increasing (absolute) 6MWT measurements at baseline were significantly associated with decreasing 1-year mortality (odds ratio [OR], 0.931/10 m; 95% CI, 0.919-0.944; P <.001). Moreover, increasing (absolute) measurements of 6MWT at follow-up were significantly associated with decreasing 1-year mortality (OR, 0.952/10-m increase; 95% CI, 0.932-0.972; P <.001).
For both absolute and relative change in 6MWT distance between initial and follow-up presentations, an increase between visits in distance walked was significantly associated with decreasing 1-year mortality (OR, 0.978/10-m increase in 6MWT between visits; 95% CI, 0.967-0.990; P <.001 and OR, 0.999/10% increase in 6MWT between visits; 95% CI, 0.998-1.000; P =.046).
The investigators noted that their support of the cutoff values was included in the most recent guidelines. They concluded that the results of the study help to explain why changes in 6MWT did not correlate consistently with prognosis in prior studies.
Disclosures: This study was funded in part by Actelion Pharmaceuticals, Bayer, and GlaxoSmithKline.
Reference
Zelniker TA, Huscher D, Vonk-Noordegraaf A, et al. The 6MWT as a prognostic tool in pulmonary arterial hypertension: results from the COMPERA registry [published online January 24, 2018]. Clin Res Cardiol. doi:10.1007/s00392-018-1207-5
