Plasma near-infrared spectroscopy for diagnosis of idiopathic Parkinson's disease: the SPIN-PD study

Aim: There are no established chemical biomarkers of idiopathic Parkinson's disease (PD). The results of a prior metabolomics-based biomarker study suggested that near-infrared spectroscopy of blood plasma samples may distinguish idiopathic PD from neurologically normal controls. Methods: Near-infrared spectroscopy was used to detect and quantify substrate modifications in blood plasma samples derived from 71 PD subjects enrolled in the PostCEPT observational study and 68 normal control subjects. Results: Near-infrared spectra values were significantly higher in the PD group compared with the control group when adjusted for age and gender (PD: adjusted mean 0.49 [95% CI: 0.45-0.53]; control: adjusted mean 0.40 [95% CI: 0.36-0.44]; p = 0.004, multiple regression). Conclusion: Near-infrared spectra of blood plasma in early-stage idiopathic PD differ from those of non-neurological control subjects. However, the degree of overlap between the groups limits the use of this technique in its present form as a PD biomarker for routine clinical practice.