Ahmed and Santosh [1] measured the serum levels of various metals in PD (n=45) and non-PD (n=42) people in South India.

They found that "Al [high in PwP], Cu [high], Fe [low], Mn [high] and Zn [low] were dominantly reponsible for the separation of PD from normal".

They went on to look at the correlation between metal ratios and PD: "Al/Cu, Al/Fe, Al/Mn, Al/Zn, Cu/Fe, Cu/Zn, Fe/Zn and Mn/Zn were increased and Fe/Mn and Cu/Mn were decreased in PD compared to healthy control".

They describe a neural network (a computing technique, ironically inspired by the working of the brain) which, taking together all the relationships, gives a 95% diagnostic accuracy. (But, note the small sample size.)

Reference

[1] Ahmed SSSJ, Santosh W (2010) Metallomic Profiling and Linkage Map Analysis of Early Parkinson's Disease: A New Insight to Aluminum Marker for the Possible Diagnosis. PLoS ONE 5(6): e11252. doi:10.1371/journal.pone.0011252
http://www.plosone.org/article/info%...l.pone.0011252

John