Editor,—The recent study by Hutton, Colver, and Mackie1 is in some respects a useful addition to our knowledge of survival in cerebral palsy. Unfortunately there are substantial problems with the paper; we note three of them below.

1. In figure 1A it appears that in the most seriously affected group, who had a Lifestyle Assessment Score (LAS) ⩾70%, there is100% survival to age 9. This scarcely seems plausible when, as the graph indicates, 20% of these survivors die in the next 9 years. The explanation is that the most severely disabled children, with LAS 70% or more, have to survive to age 5 to be assessed by LAS. Thus the severely disabled children who die before 5 have no LAS, and are excluded (actually, it appears from the graph that some children are evaluated even later than age 5).

The resulting bias could have serious consequences. For example, in a lawsuit involving a neurologically devastated 2 year old child a plaintiff may cite Hutton et al to argue for 100% survival over the next seven years.

2. Hutton et al's results show …