The purpose of the investigation governs what type
of sample should be used. In terms of biomarker
discovery, plasma is the obvious candidate, as the
ultimate goal is usually a blood test.15 However,
biomarkers are likely to occur in low relative
abundance and be massively diluted in the
circulation.15 Rigorous reproducible standard
operating procedures are essential to ensure that
samples are collected, stored and transported in an
identical manner.