Dried blood spots versus blood plasma: a comparison of two sampling methods for targeted metabolomics

Dried blood spots (DBS) are an alternative sampling method to blood plasma sampling. In contrast to blood plasma sampling, DBS are low-volume capillary blood samples obtained via pricking and collection on paper cards. DBS require less space and no cooling which is advantageous for exercise tests in the field. The aim of this project was to compare metabolite concentration measurements of DBS and blood plasma samples. Moreover, we investigated the effects of acute exercise in women and men. Methods DBS and blood plasma samples were collected from 28 fasted volunteers (13 female, age 24.9 ± 1.99 years) from the earlobe. Samples were taken at rest and directly after a graded-exercise test to exhaustion on a bicycle ergometer. Metabolite concentrations of 43 amino acids and acylcarnitines were measured via flow-injection analysis tandem mass spectrometry. Results All amino acids and 13 out of 30 acylcarnitines were quantified in the accepted LOD range (> 80% of samples) and included in further analyses. Absolute metabolite concentrations were significantly higher in blood plasma samples for 20 out of 26 remaining analytes when compared to DBS. Principal component analysis indicated a strong association between sampling method and the observed variation in our data. Correlations between DBS and blood plasma metabolite concentrations for the metabolites ranged between r = -0.107 for aspartate and r = 0.983 for octanoyl carnitine (0.587 ≥ p ≥ 0.001, n = 28). Linear regression revealed a proportional bias for 19, a systematic bias in eleven, and no bias in six out of 26 metabolites. To test for the influence of gender and exercise, we performed a two-factor repeated measures ANOVA which yielded differential results for each sampling method. In blood plasma, significant effects could be shown for 10 analytes by exercise and 4 by gender. In contrast, DBS has elucidated 23 changed metabolites by exercise and differences in gender in 10. Overall, exercise significantly changed the concentrations of a majority of analytes, and amino acids (N = 8) where metabolites which significantly differed in-between different sexes, shown predominantly in DBS. Discussion Metabolomics results of DBS and blood plasma samples moderately correlate. We therefore recommend to only use DBS e. g. in field experiments if plasma sampling and storage is impossible.      «

Dried blood spots (DBS) are an alternative sampling method to blood plasma sampling. In contrast to blood plasma sampling, DBS are low-volume capillary blood samples obtained via pricking and collection on paper cards. DBS require less space and no cooling which is advantageous for exercise tests in the field. The aim of this project was to compare metabolite concentration measurements of DBS and blood plasma samples. Moreover, we investigated the effects of acute exercise in women and men. Me...     »