Dr. Hyman M. Schipper of Jewish General Hospital, Montreal, and team reported that the pattern of metabolites in blood plasma that differentiate patients with sporadic AD from those who are cognitively healthy not only serves as a valuable biomarker but also provides further evidence that oxidative stress is involved in the systemic pathophysiology of sporadic AD.
The researchers compared plasma samples from 63 participants including 19 patients with AD, 27 participants with memory-related mild cognitive impairment (MCI) and 17 normal elderly control participants. NIRS data analysis focused on 5 spectral bands, associated with heme, R-CH, R-OH, H2O and R-NH functional groups that were sensitive to oxidative modification.
NIRS could differentiate AD patients from normal elderly controls with a sensitivity of 80% and specificity of 77%. Values of plasma samples from MCI patients ranged widely that extensively overlapped with both the AD and control groups.
Many MCI patients showed spectra identical to those observed in the AD cohort, Dr. Schipper told Reuters Health. This strongly suggests that the biomarker may be sensitive to AD even in pre-clinical stages. We are following the MCI cohort to determine the accuracy of the biomarker as a prognosticator of AD in this setting.
The authors reported that previous research could differentiate individuals with idiopathic Parkinson’s disease from normal elderly controls with about 75% accuracy using NIRS and Raman spectroscopy of plasma.
Thus, although many human neurodegenerative conditions might feature systemic oxidative stress, it is conceivable that the nature of the putative oxidative substrate modifications, and hence the biospectra, may differ substantially among the various clinical entities, they write.
Although valuable as a proof of concept, research findings likely underestimate the full neurodiagnostic potential of NIRS.
