Validation of a rapid measure of blood PUFA levels in humans.

An assay involving a finger stick and filter paper blood spotting was developed to determine polyunsaturated fatty acid (PUFA) levels in blood. Capillary whole blood from a finger stick was blotted on antioxidant impregnated filter paper, air dried, saponified and methylated using sodium hydroxide and boron trifluoride in methanol. The method differed from those described previously because separation of plasma and red blood cells (RBCs) was not needed, thin-layer chromatography (TLC) was not required to separate phospholipids, initial extraction of lipids before transesterification was not necessary, and the fatty acid methyl ester (FAME) method was able to methylate steryl esters, free fatty acids, and sphingomyelins. Twenty-six subjects provided blood samples by finger stick and venipuncture. Levels of long-chain polyunsaturated fatty acids (LC-PUFA) from capillary whole blood were correlated with those from RBCs and PLs in venous blood (P < 0.001, R(2) ranged from 0.64 to 0.86). Although highly significant (P < 0.002), the R(2) values for the correlation between arachidonic acid (ARA) levels in capillary whole blood with ARA levels in RBCs and plasma phospholipids (PLs) were relatively lower (R(2) = 0.31-0.41, respectively). Results indicate that the described finger stick assay represents a fast, reliable method to measure specific LC-PUFA levels.