Dougan MM, et al. - The detectability, reliability, and distribution of metabolites measured in pre-diagnostic plasma samples was investigated in a pilot study of women recruited in the Northern California site of the Breast Cancer Family Registry. For this research, 45 cases diagnosed with breast cancer at least 1 year after the blood draw and 45 controls were included. According to the results, assays are reproducible for many metabolites and there was minimal laboratory variation for the same sample, yet a large between-person variation. Differences between cases and controls in some metabolites infer that a well-powered large-scale study would be likely to identify meaningful differences to provide a better understanding of breast cancer etiology despite small sample size.