The DiPALS report may be a study incurred of a false negative sample; In ALS a treatment group may appear to fair less successfully than the control group when the patient count is small. I have seen cases where a patient lasts only six months from disease onset to cases where a patient remains alive after fifty years from disease onset. So the patients lived less long in the treatment group; did they live longer than they would have? Efficacy is about whether they lived longer with than without the treatment.

Given a group of 37 ALS patients, we might expect to see seven slow regressors and presumably seven fast regressors (yet I know of very little literature on fast regressors).