CHIT1 and amyotrophic lateral sclerosis: However, it should also be noted that a CHIT1 polymorphism has been identified that reduces the CHIT1 levels in CSF of patients with ALS.180 A contrasting study using both mass spectrometry and ELISA showed that CSF CHIT1 was significantly higher in ALS compared with disease and healthy controls, while CHI3L1 was higher in ALS and disease controls than healthy controls, and the rate of increase in these biomarkers correlates to disease progression.65