Plasma protein profiling: unique and stable features of individuals.

Carefully controlled ZipTip extraction of diluted human plasma or serum was combined with MALDI-TOF-MS to produce highly reproducible protein profiles. Components detected included apolipoproteins CI, CII and CIII as well as transthyretin and several isoforms of each protein that are created by glycosylation or other modification and by proteolytic processing. Profiles of healthy individuals all contained the same 15 components. Others were found in plasma from individuals with disease. Profiles were analyzed by peak ratios within the same spectrum. Reproducibility for multiple assays was generally 4 to 10%. Within the healthy population, a given peak ratio occurred with a range of about fourfold. However, peak ratios of multiple samples from the same individual showed a much lower range, typically +/-10%. In fact, each individual displayed a personal protein profile that changed very little over time. Because of the stability of protein profiles over time within individuals, these results suggest further studies may discover that certain profile characteristics or changes in an individual's profile may be a sign of current or future disease, even when the altered profile remains within the range for healthy individuals.