The Friedman test showed that plasma GFAP levels in PD increased significantly (p < 0.001) over the 2-year follow-up (baseline: mean [SD]: 69.80 [36.18] pg/mL, 2-year follow-up: mean [SD]: 74.12 [40.79] pg/mL; Fig. 1A, C, and Additional file 1: Table S1). The gene discussed is GFAP; the disease is Parkinson disease.