Application of dried blood spots to determine vitamin D status in a large nutritional study with unsupervised sampling: the Food4Me project

Abstract

An efficient and robust method to measure vitamin D (25-hydroxy vitamin D 3 (25(OH)D 3 ) and 25-hydroxy vitamin D 2 in dried blood spots (DBS) has been developed and applied in the pan-European multi-centre, internet-based, personalised nutrition intervention study Food4Me. The method includes calibration with blood containing endogenous 25(OH)D 3 , spotted as DBS and corrected for haematocrit content. The methodology was validated following international standards. The performance characteristics did not reach those of the current gold standard liquid chromatography-MS/MS in plasma for all parameters, but were found to be very suitable for status-level determination under field conditions. DBS sample quality was very high, and 3778 measurements of 25(OH)D 3 were obtained from 1465 participants. The study centre and the season within the study centre were very good predictors of 25(OH)D 3 levels (P < 0·001 for each case). Seasonal effects were modelled by fitting a sine function with a minimum 25(OH)D 3 level on 20 January and a maximum on 21 July. The seasonal amplitude varied from centre to centre. The largest difference between winter and summer levels was found in Germany and the smallest in Poland. The model was cross-validated to determine the consistency of the predictions and the performance of the DBS method. The Pearson's correlation between the measured values and the predicted values was r 0·65, and the SD of their differences was 21·2 nmol/l. This includes the analytical variation and the biological variation within subjects. Overall, DBS obtained by unsupervised sampling of the participants at home was a viable methodology for obtaining vitamin D status information in a large nutritional study.

Associations of vitamin D status with dietary intakes and physical activity levels among adults from seven European countries: the Food4Me study

“…Participants were recruited in 7 European countries (Ireland, the Netherlands, Spain, Greece, the UK, Poland and Germany) using identical standardised protocols in all recruitment centres, as described in detail elsewhere [17]. In brief, local and national advertising of the study via the Internet, radio, newspapers, posters, e-flyers, social media and word of mouth, were used to recruit adult men and women.…”

“…A second online informed consent form was completed before randomisation to the intervention study only for participants who met the inclusion criteria. A total of 1,607 study participants aged ≥18 years were recruited [17].…”

“…To ensure that procedures were similar, standardized operating procedures were adopted in the recruiting centres and for all study procedures and researchers were trained in their use [17]. Two screening questionnaires, including a Food Frequency Questionnaire (FFQ) that was specifically developed and validated for the purposes of this study [19,20], were used to identify participants for the Food4Me study.…”

“…Categories for "Students" and "Retired and unemployed" were also added. Participants also provided health and anthropometric data at screening and detailed information on dietary intake and food preferences [17]. Anthropometric and PA data, as well as blood and buccal cell samples were collected from all study participants and the latter were used for metabolic marker analysis and genotyping, respectively.…”

Nutrition, epigenetics and health through life

“…Whilst these new technological approaches raise both ethical and practical issues (Ramagopalan & Rakyan 2013), they have substantial potential in nutrition research. The use of DBS is not restricted to neonatal diagnosis, and increasingly, this approach to blood collection is being used in large epidemiological studies (Hoeller et al 2016) because of the much reduced costs for blood collection (which can be carried out by the participants themselves without the need for expensive phlebotomists) and for storage (DBS require much less space than does liquid blood and do not need ultralow temperature). Such approaches may advance studies of nutritional epigenomics in resource-poor regions of the world, help to reduce global inequalities in research capacity and accelerate the translation of research outcomes to public health benefit.…”