Effect of storage temperature in a Cambodian field setting on the fatty acid composition in whole blood.

Fatty acid analysis requires standardized collection and storage of samples, which can be a challenge under field conditions. This study describes the effect of storage temperature on fatty acid composition in two sets of whole blood samples collected from 66 children in a rural area in Cambodia. The samples were stored with butylated hydroxytoluene at -20 °C and -80 °C and the latter required extra transfers due to storage facility limitation. Fatty acid composition was analyzed by high-throughput gas-chromatography and evaluated by paired t-tests and Bland-Altman plots. Total amounts of fat in -20 °C and -80 °C samples did not differ, but there was relatively more highly unsaturated fatty acids (15.8 ± 2.7 vs. 14.4 ± 2.5%, p < 0.001) and a lower n-6/n-3 ratio (6.4 ± 1.4 vs. 6.9 ± 1.4, p < 0.001) in the -20 °C samples. Our results indicate that the importance of storage temperature should be evaluated in the context of storage facility availability and risk of temperature fluctuations during transport.

EPA and DHA levels in whole blood decrease more rapidly when stored at -20 °C as compared with room temperature, 4 and -75 °C.

High-throughput n-3 fatty acid profiling is enabled by collection techniques such as venous whole blood and fingertip prick (FTP) sampling, but the resulting increased sample numbers increases storage demand. Highly unsaturated fatty acids (HUFA) in erythrocytes are susceptible to oxidation, but this tendency is poorly characterized in venous and FTP whole blood. Presently, whole blood samples with low and high n-3 content collected with ethylenediaminetetraacetic acid were stored on chromatography paper with and without BHT pre-treatment for up to 180 days at different temperatures (room, 4, -20, -75 °C). Whole blood prepared with heparin and BHT and stored in cryovials was also examined. Eicosapentaenoic acid (EPA, 20:5n-3) + docosahexaenoic acid (DHA, 22:6n-3) is relatively stable when stored at -75 °C under various conditions but rapidly decreases in whole blood when stored at -20 °C. At -20 °C, BHT + heparin prepared whole blood can prevent decreases in cryovials up to 180 days but BHT only slows the decreases on chromatography paper. Surprisingly, whole blood stored at 4 °C and room temperature was less susceptible to decreases in EPA + DHA as compared with -20 °C storage. Assessments of n-3 blood biomarkers indicate the % n-3 HUFA in total HUFA was more stable as compared with the sum of the relative % of EPA + DHA. In conclusion, FTP and venous whole blood for fatty acid analysis should be stored at -75 °C whenever possible. In the absence of -75 °C storage conditions, BHT should be added and 4 °C or room temperature appear to be better alternatives to -20 °C.