Here is what I found for you…For the 6MWT, from what I understand, it’s not necessarily about the specific number of meters lost, it’s about the percentage the patient is below the predicted distance they should be able to walk. This threshold is 55% below the predicted distance (approximately 325 meters). Once children reach this threshold, a high percentage decline >10% over the subsequent year, quickly on their way to losing ambulation. Reaching this threshold value doesn’t necessarily help predict when a child will lose ambulation, but it is an indicator that they are on their way, likely within the next year or two.
The 30 meter MCID is helpful for drug research studies to help determine what change scores are important.
I also have a message out to an expert. If she says anything different, I’ll let you know!
McDonald CM, Henricson EK, Abresch RT, et al. The 6-minute walk test and other endpoints in Duchenne muscular dystrophy: longitudinal natural history observations over 48 weeks from a multicenter study. Muscle Nerve. 2013;48(3):343-356. doi:10.1002/mus.23902