However, in prior reports in the literature, where ELISA techniques had been optimized for the detection of MMP-9 in the CSF among recruited confirmed healthy adults (n = 27, median age = 33 years, range = 26–43 years of age), the levels of MMP-9 ranged from 0.156 to 0.189 ng/ml, which is lower than our observed mean MMP-9 levels for either the ALS (0.25 ng/ml) or OND (0.22 ng/ml) groups [28]. This evidence concerns the gene MMP9 and amyotrophic lateral sclerosis.