In order to evaluate the utility of HO-1 as a candidate biomarker of PD, an ROC curve was generated to distinguish PD patients in general from controls; the optimal cutoff value was found to be 2.255 ng/ml (sensitivity = 68%, specifity = 61.7%, AUC = 0.627, p = 0.006); the cutoff value for early-stage PD was 2.245 ng/ml (sensitivity = 66%, specifity = 66.7%, AUC = 0.654, p = 0.004). Here, HMOX1 is linked to Parkinson disease.