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There are some subtle clinical tests, for example a decline in visual color perception (interestingly, the blue-sensitive cells!) but they are probably too complicated to be done as a pre-screening routine. The PET scan or the SPECT scan is effective, they work by observing the uptake of dopamine that has been tagged with a radioactive tracer, but probably neither technique is within the reach of an ordinary clinic, as the equipment costs megabucks. Cheers, Joe J. R. Bruman (818) 789-3694 3527 Cody Road Sherman Oaks CA 91403