P.2.6 Comparison of 6MWD and person-reported functional measures in boys with Duchenne muscular dystrophy aged 4–12 years

30-m change in walking ability by 6MWT may not always be clinically meaningful from a quality of life perspective. Differing changes in ability may contribute to patient-reported function at differing levels of ability. We describe correlation between measures, 1-year change in measures, and correlation of 1-year changes between measures for 6MWT, PedsQL and POSNA PODCI in 24 4–12 y.o. ambulatory DMD and 36 typical controls, and determine if minimal clinically-importand differences (MCID) of HrQOL measures contribute to different estimates of walking distance change at differing levels of ability. PedsQL total/physical function and PODCI global, transfer/mobility and sports/physical function demonstrated significant differences between DMD and controls ( p r  = 0.79). In DMD 6MWT distance weakly correlated with PedsQL. In DMD, 6MWT and PODCI global and transfer and mobility demonstrated significant one-year change and exceeded the amount of change representing MCID. In DMD, 6MWT change highly correlated with change in PODCI global and PODCI transfer/mobility scores ( r  = 0.76 and r  = 0.93). PODCI global and PODCI transfer/mobility scales provided the best estimates of 6MWT performance. A “meaningful” 4.5 point change in a low PODCI transfer/mobility score of 30–34.5 was associated with a 5.6 m 6MWT change from 150.3 to 155.9 m. At PODCI levels closer to normative levels changes in 6MWT distance needed to affect a “meaningful” change in PODCI scores were associated with a 6MWT change of almost 46 m. At lower levels of function, smaller increases 6-min walk distance result in meaningful change in quality of life. At higher levels of function, larger increases may be necessary to achieve the same QoL effect.