The use of the 12 minute walking test in assessing the effect of oral steroid therapy in patients with chronic airways obstruction

Abstract

The reproducibility of the 12 minute walking distance (12MD) was assessed in ten men with chronic airways obstruction, and the 12MD was used, together with spirometry, transfer factor and three subjective assessments of breathlessness to evaluate the effects on respiratory function of prednisone 30 mg daily given orally in double-blind placebo-controlled fashion for two weeks. Like others, we found the 12MD reproducible on a single day with a mean variation of 3.1%. Tests performed two weeks apart showed greater variability ranging from 0.2% to 30.9%, (mean 9.1%). During placebo and prednisone therapy the 12MD and assessments of breathlessness correlated significantly with each other and with TLCO, but not with spirometry. Following steroid therapy there was a significant increase in mean TLCO but no significant change in 12MD, spirometry or subjective assessments. Changes in 12MD and TLCO correlated significantly with each other and with changes in subjective assessments. Changes in FEV 1 correlated with changes in breathlessness, and also with variability in FEV 1 while receiving placebo. Individuals with the greatest changes in 12MD and FEV 1 were those with the greatest variability on placebo. The variability of the 12MD and FEV 1 should be measured in individuals before using these tests to assess response to steroid therapy.