William S Harris and Jason Polreis
Background: The roles that the omega-3 fatty acids play in health and disease remains unclear. The conduct of epidemiological studies to explore this relationship can be facilitated by the use of dried blood spots (DBS) for sample collection and shipment. The Omega-3 Index [i.e. erythrocyte levels of the two major marine-derived omega-3 fatty acids, eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA)], is an emerging risk factor for cardiovascular disease mortality. The purpose of this report is to describe how the Omega-3 Index can be derived from an analysis of DBS fatty acid levels.
Methods: A comparison of the Omega-3 Index and DBS EPA+DHA levels was conducted in 147 random samples received in the laboratory, and in 106 samples prospectively collected and processed through the US mail. The “in field” coefficient of variation of the DBSderived Omega-3 Index was calculated from 147 duplicate samples collected in an epidemiological study in Mexico. The stability of DBS EPA+DHA levels when collected on antioxidant-treated paper was tested for 44 days at room temperature, and for up to 4 years in the freezer.
Findings: We found that the correlation between the DBS EPA+DHA level and the Omega-3 index was 0.97 (p<0.0001), hence the latter can be accurately estimated from the former. As a storage and transport system, DBS cards (pretreated with an antioxidant cocktail) provide protection from degradation for blood EPA+DHA levels (i.e. >15% loss) for at least 6 weeks at room temperature, 4 weeks in a refrigerator, 3 years at -20°C and 4 years at -80°C.
Conclusion: These data confirm the utility of this DBS system for estimating the Omega-3 index.
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