Statistical aspects of quantitative image analysis of β-amyloid in the APP^V717F transgenic mouse model of Alzheimer's disease

Cerebral β-amyloidosis is a central part of the neuropathology of Alzheimer's disease (AD). Quantitation of β-amyloid plaques in the human AD brain, and in animal models of AD, is an important study endpoint in AD research. Methodologic approaches to the measurement of β-amyloid in the brain vary between investigators, and these differences affect outcome measures. Here, one quantitative approach to the measurement of β-amyloid plaques in brain sections was analyzed for sources of variability due to sampling. Brain tissue was from homozygous APP^V717F transgenic male mice. Sampling variables were at the mouse and microscopic slide and field levels. Results indicated that phenotypic variability in the mouse sample population was the largest contributor to the standard error of the analyses. Within each mouse, variability between slides or between fields within slides had smaller effects on the error of the analyses. Therefore, when designing studies of adequate power, in this and in other similar models of cerebral β-amyloidosis, sufficient numbers of mice per group must be included in order for change in mean plaque burden attributable to an experimental variable to outweigh phenotypic variability.