CST3 and Nephropathy: The ALS group was found to have the lowest mean level of serum creatinine of all of the groups, which was significantly lower than the HC (p = 0.0345) and nephropathy groups (p = 0.0064), indicating again that the ALS group do not exhibit signs of renal dysfunction., We next examined the levels of serum cystatin C and calculated the eGFR for all of the disease groups.