NEFL and amyotrophic lateral sclerosis: Specifically, serum levels of neurofilament light chains (NFL) (SMD: 1.57, 95% CI: 1.29 to 1.85) (Sferruzza et al., 2022), CSF NFL levels (SMD: 2.06, 95% CI: 1.61 to 2.51) (Sferruzza et al., 2022), and serum ferritin levels (SMD: 0.66, 95% CI: 0.50 to 0.83) (Cheng et al., 2021) were significantly higher in ALS patients, while uric acid levels (SMD: −0.72; 95% CI: −0.98 to −0.46) (Wang et al., 2019) were lower in ALS patients compared to controls.