Measurement of cystatin C levels in the cerebrospinal fluid of patients with amyotrophic lateral sclerosis.

The diagnosis of amyotrophic lateral sclerosis (ALS) is mainly based on clinical and electrophysiological features. It is yet to be confirmed if cystatin C (Cys-C) can be a candidate diagnostic biomarker for ALS. This retrospective study aimed at investigating the changes in the level of Cys-C levels in the cerebrospinal fluid (CSF) of Chinese patients with ALS. CSF and serum samples obtained from patients with ALS, healthy controls (HC) and neurodegenerative disease controls from March 2012 to May 2014 were analyzed for levels of Cys-C using an immunoturbidimetric assay. The results were checked for the presence of meaningful correlations between Cys-C levels and variables such as the age of onset, site of symptoms onset, disease duration, and amyotrophic lateral sclerosis functional rating scale revised (ALSFRS-R) score, forced vital capacity (FVC) and rate of ALS disease progression. There was no difference in the Cys-C levels in CSF and serum between patients with ALS and controls. However, the serum Cys-C levels correlated with the ALSFRS-R score and the site of symptoms onset. The statistical analysis exhibited reduced levels of serum Cys-C in Upper limb-onset ALS (U-ALS) compared to Lower limb-onset ALS (L-ALS). The present data demonstrate that the level of Cys-C in CSF should not be considered as a biomarker of ALS. Cys-C in serum may be useful as an indicator of the severity of disease and site of symptoms onset although the specificity of serum Cys-C levels in ALS was not significant.