Scientific Concept of the National Cohort (status ... - Nationale Kohorte

A.3
A.3 Study design
A.3.5 Collection, preanalytical processing, storage, and retrieval of biomaterials
A.3.5.1 Overview and general principles
The collection of biomaterials for future phenotyping at the molecular level represents a
basic component central to the entire National Cohort. For such molecular phenotyping, a
comprehensive array of biomaterials in optimal quality is indispensable.
Optimal preservation of quality relies on minimizing preanalytical artiifacts that may be
incurred during specimen collection, primary processing, transport and/or storage of the
samples, including:
� Artifacts due to cell lysis, which promotes release of intracellular components with
concentrations that are several magnitudes higher in the intracellular than in the extracellular
compartment. This is exemplified by release of potassium, lactate dehydrogenase,,
or catecholamines from red blood cells in hemolysis, or of proteolytic
enzymes from leukocytes, which not only alters their serum or plasma concentration
but may also degrade target analytes such as insulin.
� Artifacts due to cell metabolism, exemplified by the decrease in glucose concentration
upon prolonged storage of blood, or the continuing in vitro production by cells of the
amino acid homocysteine (a marker of cardiovascular risk) by blood cells in vitro
� Artifacts due to the enzymatic degradation of molecular species upon prolonged exposure
to 4°C or higher.
� Molecular artifacts due to repeated freezing and thawing.
Given the huge number of potential analytes and taking into account that analytes of interest
and techniques may both change over the study period to an extent that cannot be
foreseen today, it is mandatory to avoid all artifacts. This requires:
� The prompt and complete separation, ideally within 1 h of collection, of all particulate
components of full blood to obviate the cell-derived artifacts detailed above.
� No delay in preparing aliquots and freezing to obviate enzymatic degradation during
prolonged transportation at 4°C or higher.
� Volumes small enough (190 µl) to guarantee single use only as opposed to repeated
thaw–freeze cycles necessarily implicated in the storage of larger volumes.
High quality and wealth of the National Cohort Biobank will be assured by the following
major principles:
� Local, and not centralized processing of blood, urine, and other biomaterials, which
is complete enough to reach the level of ready-prepared small aliquots that can be
transported to the central storage unit on dry ice in a deep-frozen state (except for
viable blood cells). This would obviate the enzymatic disintegration incurred upon
prolonged exposure to 4°C or higher.
� Automation of all steps in preparation, storage, and retrieval of stored materials, promoting
strict adherence to SOPs, maximizing reproducibility, and obviating artifacts
that inevitably occur during manual processing in the long run due to individual failure.
Thus, each study center will be equipped with a liquid handling platform.
� Storage of biomaterials from all participants throughout Germany in one central automated
biorepository and decentralized back-up storage.
� The strategy also involves storing many small aliquot volumes to avoid thaw–freeze
cycles and thereby to increase sample quality.
� The quality assurance and quality control of the collection and processing of biosamples
is described in Sect. A.5.6. Detailed SOPs and specific training materials for
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