• Parkinson’
• s disease
• SPECT

Dr Snow is right to be cautious in his optimism concerning the use of functional imaging markers in neuroprotection studies in Parkinson’s disease¹ as storm clouds gather^2,3 over the methods and interpretation of CALM-PD and REAL-PET. The concerns, however, are not limited to the effect of drug treatment on ligand uptake. Most importantly we need to ask the weight that should be placed on the result of functional imaging studies when they are not supported by the accompanying clinical data. In addition, there are concerns about the ability of the methods for accurately monitoring progression. The key requirements for a PET or SPECT method to be used in assessing progression are sensitivity to clinical change and reproducibility.⁴ There are no data concerning either from the study of Winogrodzka and colleagues,⁵ the authors quoting reproducibility data from Seibyl et al.⁶ These data need to be presented for the benefit of the readership. The mean (SD) scan to scan variability in a group …