Therapeutic trials conducted in Alzheimer's disease have benefited fro
m the standardization of diagnostic criteria based on internationally
recognized scales (DSM III-R, NINCDS - ADRDA) which ensure more valid
inclusions. Well specified exclusion criteria are also of the utmost i
mportance, in particular depression, vascular dementia and concomitant
psychotropic drugs. Cognitive and/or functional scales allow an appre
ciation of the severity of the disease. Due to the heterogeneity of Al
zheimer's disease stratification methods on identified prognostic fact
ors i.e. aphasia, extrapyramidal symptoms should be performed. Selecti
on of responders during an enrichment phase has still to be discussed.
Multicentric studies become imperative because of the large number of
patients required and the difficulties in selecting the adequate pati
ents. These raise the issues of investigators' experience, coordinatio
n and between center variability.