Sampling and processing of fresh blood samples within a European multicenter nutritional study: evaluation of biomarker stability during transport and storage

Introduction: Analysis of several biological markers improves the quality and physiologic comprehension of data obtained in epidemiological nutritional studies. Aim: To develop a methodology that guarantees the centralized analysis and quality assurance of the most relevant blood parameters from fresh blood samples in adolescents in a European multicenter study. Materials and methods: Stability of selected nutrients and biomarkers (vitamins, fatty acids, iron metabolism and immunological parameters) chosen with respect to time and temperature of sample transport and storage was evaluated as part of the pilot study of the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) project. Results: Routine biochemistry and iron status parameters included in the HELENA Cross-Sectional Study (CSS) protocol could be analyzed within 24 h from fresh blood samples without any stability problems (coefficient of variation (CV) < 5%, P < 0.05). However, stability tests for lymphocyte subpopulations, vitamin C and fatty acids showed that they are very unstable at room temperature without any treatment. Therefore, a special handling for these samples was developed. Vitamin C was stabilized with metaphosphoric acid and transported under cooled conditions (CV 4.4%, recovery rate > 93%, P > 0.05). According to the results, a specific methodology and transport system were developed to collect blood samples at schools in 10 European cities and to send them to the centralized laboratory (IEL, Bonn, Germany). To guarantee good clinical practice, the field workers were instructed in a training workshop and a manual of operation was developed. Conclusion: The handling and transport system for fresh blood samples developed for the European multicenter study HELENA is adequate for the final part of the HELENA-CSS and will provide, for the first time, reference values for several biological markers in European adolescents.