MMP9 and amyotrophic lateral sclerosis: While there was no correlation between MMP-2 and creatinine levels, there was a statistically significant positive correlation between total serum MMP-9 and serum creatinine in ALS using both Pearson’s product–moment correlation (p = 0.028) and Spearman’s rank correlation (p = 0.005) analysis (Figure 7A).