MMP3 and Parkinson disease: There were statistically significant differences in MMP3 levels among the three groups (early-stage PD patients, advanced-stage PD patients and healthy controls) [12.56 (9.30, 17.44) vs. 15.31 (8.96, 25.49) vs. 15.37 (11.33, 24.41) ng/ml; P = 0.017].