Qualitative data assessment revealed that short survival times were most strongly associated with the lowest cystatin C levels and, for this reason, we selected a cut-off value of 2.75 μg/ml to separate the ALS patients into a smaller low cystatin C group (n = 11) and a larger high cystatin C group (n = 21). Here, CST3 is linked to amyotrophic lateral sclerosis.