Prognostic value of the 6min walk test in bronchiolitis obliterans syndrome

Bronchiolitis Obliterans Syndrome (BOS) complicates the course of many lung transplant recipients. It carries significant risk of morbidity and mortality, but its course is difficult to characterize. We evaluated the prognostic utility of the 6min walk test (6MWT) obtained after the onset of BOS in 42 patients. This was compared to the prognostic significance of changes in the FEV1. The median time between the onset of BOS and the 6MWT was 109 days. The median decline in the FEV1 from baseline to BOS onset was 25.7%, while the median change over the ensuing 3 months was 12.5%. Neither of these was predictive of subsequent mortality. The 6MWT yielded averages in the resting saturation, lowest saturation, distance walked and maximal Borg scores of 97%, 90.2%, 323m and 2.35, respectively. The best of these parameters in discriminating survival was the distance. Patients who walked further than 330m had a median survival of 1178 days versus 263 days for those who walked less (p<0.0001). We conclude that the 6MWT provides important prognostic information in patients with BOS and might perform better than spirometry. Use of this test might allow different clinical phenotypes to be discerned.