Introduction Exercise capacity is predictive of mortality in CF. Objective measurement of daily physical activity may be related to exercise capacity and both may be useful outcome measures in interventional trials. Participants in this CF study had a field-based estimate of exercise capacity and objective measurement of physical activity at each study visit.
Methods Participants wore a pedometer for 7 days prior to each visit. At each visit, London patients performed a standard incremental shuttle-walk test and Edinburgh patients a modified shuttle test (in which running was allowed). Data are expressed as mean (SD).
Results Data were analysed from 192 patients over 648 visits. Age at enrolment was 24 (11.9) years (London) and 20.8 (9.9) (Edinburgh) (p=0.052); FEV1 was 67 (17.7)% and 79 (19.5)% for each site respectively (p<0.001). Daily step count at visit 1 was 7491 (2887) in London and 8872 (4089) in Edinburgh (p=0.04) and this difference persisted across subsequent visits. The coefficient of variation (CV) in step counts between visits was 21.3%. Number of shuttles completed in London was 61 (15), and Edinburgh 90 (33) with no trend over the four visits (CV=10 and 16% respectively). In Edinburgh there was a correlation between mean step count and the number of completed shuttles (r=0.46, p<0.001). Step count from both sites, and the number of shuttles completed in Edinburgh, correlated with FEV1 % predicted (r=0.24, p<0.001 and r=0.27, p<0.001 respectively) and with age (r=−0.28, p<0.001 and r=−0.30, p<0.001 respectively). Such correlations were either weaker or not observed in London, however, in this group, number of shuttles correlated with height (r=0.51, p<0.001).
Conclusions No changes were detected in exercise capacity or daily activity levels over time. Between site differences were observed in both measures; however, these populations also differ in age and FEV1. The modified shuttle test performed in Edinburgh appeared to better correlate with clinical markers than the standard incremental shuttle test performed in London, and is independent of height. We believe that testing exercise capacity is important in CF and we plan to investigate the other testing methods in the run up to our Multi Dose Gene Therapy Trial.
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Funding Funded by the UK CF Trust.
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