Quantitating fatty acids in dried blood spots on a common collection card versus a novel wicking sampling device

Blood biomarkers of n - 3 polyunsaturated fatty acids can serve as indicators of dietary intake and benefits and/or disease risk. The use of dried blood spots for fatty acid analyses is increasing but most of the reported data is qualitative (relative percentages of total fatty acids). The ability to quantitate concentrations of fatty acids on a common blood spot collection card and a novel wicking device designed to collect 10 µL of blood was compared with a wet blood sample in ten young adult participants. Prior to this comparison, the collection materials were screened for contaminants by gas chromatography with flame ionization and liquid chromatography/tandem mass spectrometry, and the blood volume and blood spot area relationship of the collection card was confirmed using technical replicates. Palmitate and stearate were detected as free fatty acids on both collection materials and as lysophosphatidylcholines on the wicking device. The low amounts (<1.0 µg) did not affect the quantitation of these fatty acids in either material. The relationship between blood volume and blood spot area was linear (r = 0.99, p < 0.001) and it was determined that a 6 mm hole punch contained 9.6 µL of blood. When compared with wet blood, the fatty acid determinations from the dried blood spots were largely similar although there were some minor differences in low abundant fatty acids. Quantitative fatty acid determinations of dried blood spots are possible and should be reported along with relative percentage data to improve interpretation in the future.