Determination of n-3 index and arachidonic acid/eicosapentaenoic acid ratio in dried blood spot by gas chromatography

Background: Clinical and epidemiological studies suggest that analysis of the polyunsaturated fatty acids (PUFAs) is essential to evaluate nutritional requirements and disease risk. We describe a simple, sensitive and non-invasive method for estimating the n-3 index and arachidonic acid (AA)/eicosapentaenoic acid (EPA) ratio in dried blood spots (DBSs). Experimental: After obtaining DBSs on a spot card, PUFAs were transesterified (direct, acidic transesterification) and subsequently extracted with n-hexane. Gas chromatography with flame ionization detection (GC-FID) was used to analyze the extracted PUFAs, and then n-3 index and AA/EPA ratio were calculated. Method validation showed satisfactory precision and linearity. Conclusion: This analysis is simple and reliable to estimate PUFA status, and it was successfully applied to samples from 20 subjects, demonstrating its applicability.