A demonstration of the advantages of immunostaining in the quantification of amyloid plaque deposits.

Extracellular amyloid deposits are a feature of both Alzheimer type dementia and the 'normal' aging process. Quantification of amyloid plaque deposits may well be useful in distinguishing between the senescent changes associated with 'normal' aging and the pathological processes underlying dementia. To determine the most reliable and reproducible method for visualisation of the amyloid we have compared conventional silver staining techniques with beta-amyloid immunocytochemistry on a large sample of post-mortem brain tissue from both demented (n = 15, age range 60-87) and non-demented (n = 65, age range 14-99) patients. The degree of amyloid deposition was rated on a four point scale and ratings for the two techniques were significantly correlated (P less than 0.01). However, the immunocytochemical approach has a number of distinct advantages for quantification. The antibody to beta-amyloid is highly specific and does not stain neurofibrillary tangles or background features, it is considerably more sensitive than silver staining in highlighting diffuse amyloid deposits and, perhaps most importantly, it produces high contrast staining which allows easier image digitisation and subsequent computer image analysis.