Whole blood and RBCs (red blood cells) are different starting materials and the EPA+DHA content of each is different, but highly correlated. Based on multiple experiments, OmegaQuant has derived a mathematical equation that converts the DBS EPA+DHA value into the corresponding RBC value (which is the Omega-3 Index). Therefore, the sum of EPA and DHA in the DBS report will usually be slightly different from the Omega-3 Index.