On the in-vivo ex-vivo threshold: significant IPE associated with human blood sampling and handling

Abstract The conditions inside the vessels of the living human organism are different from those in the external environment outside the human body. Sampling and handling procedures must ensure that these in vivo conditions are preserved as well as possible even though invasive techniques must be used. However, such procedures will trigger biological processes, which are continued during the sample handling, altering the state and even the concentration of analytes. Thus routine blood collection will inevitably result in activation of the coagulation system, with the potential for highly significant increment preparation errors (IPE) if not compensated properly. We discuss the difficulties encountered when dealing with the in vivo–ex vivo interface being established when sampling blood for analysis. Physical sampling and the subsequent preparatory handling of blood increments from human individuals are shown to be critically dependent upon standardised procedures in order to obtain representative samples. In particular, we here focus on pre-analytical conditions affecting the coagulation system in the human body. In this context, blood sampling IPE may severely influence the outcome of the determination of many sensitive analytes. The samples collected are used for analytical determination of numerous biochemical quantities, and each of these may in fact require specific collection or handling procedures, but international guidelines are only available for the most common biochemical quantities. However, even the recommendations given in these guidelines are not necessarily evidence-based and may not suffice for all quantities to be determined. There is thus a need for further research and standardisation, which per force must include theory of sampling (TOS). These problems have prompted us to establish a new interdisciplinary collaboration between our two disciplines in order to elucidate this interesting sampling terra incognito.