Biological Samples—Standard Operating Procedures for Collection, Shipment, Storage and Documentation

Abstract

The collection of morning urine, stool, capillary and venous blood was a central component of the IDEFICS/I.Family studies to investigate the metabolic health of children, to assess gene expression of related genes, to determine correlates of bone health and to validate nutritional intake with biochemical markers. Saliva samples were used as a source of deoxyribonucleic acid (DNA) for genetic analyses but also to measure cortisol levels as an indicator of chronic stress. Stool samples were collected to assess the association of health outcomes like obesity with the gut microbiome. Considerable efforts were undertaken to ensure standardisation of sample collection procedures as well as pre-analytics, shipment, storage and laboratory analysis across all eight countries. Sample collection and processing were usually done outside a clinical setting, often in temporary recruitment centres set up for the study in schools or kindergartens. In order to ensure a fail-safe fieldwork and to optimise compliance by participating children, robust and minimally invasive procedures were deployed despite their higher costs as compared to procedures commonly used in a clinical setting, e.g. a point-of-care analyser requiring only one drop of capillary blood. Quality management included the provision of detailed standard operating procedures (SOPs) to the field staff, central training, several quality control measures including site visits, establishment of a central biorepository, choice of a central certified clinical laboratory and documentation of all process steps from collection to analysis in a central laboratory information system. By collecting and analysing biological samples in a large and diverse group of small children from all over Europe, the study did not only provide important insights into the aetiology of diet- and lifestyle-related disorders and it also generated population-based, age-specific reference values obtained from healthy children that will help to improve paediatric practice in the future.