Frequently Asked Questions for Researchers


A. It differs in several ways.

First, the sample types we typically use (red blood cells or dried blood spots versus whole plasma or plasma phospholipids). Each of these sample types has a unique fatty acid profile, so you cannot compare the EPA+DHA level in RBCs to the EPA+DHA level in plasma, or in plasma phospholipids – the numbers will be quite different, even from the same lab. So regardless of which lab you choose to work with, you should always order the same type of test if you want to be able to track trends in the same patient over time. We focus on RBC and whole blood (dried blood spot) analyses because from either one we can provide the Omega-3 Index. These metrics provide the best reflection of tissue omega-3 fatty acid status. In addition, there is considerably more day-to-day variation in the plasma tests than in the RBC – (or whole blood) – based tests, and an acute load of omega-3 fatty acids (from fish or capsules) will significantly perturb the plasma-based markers but not the RBCs. Nevertheless, for research purposes, OmegaQuant can and does analyze any sample type based on the client’s needs and sample types available.

B. The uniqueness of the specific method we use

Second, even if you order the RBC-based assay from two different labs, there is no guarantee that you’ll get the same answer. That’s a big problem. The reason is that, unlike serum cholesterol or glucose or calcium, there is no standardized method (i.e., internationally recognized gold standard) to which all labs must peg their assays. There is no standard test material to which all labs are required to conform. So your EPA+DHA, for example, might be 6.7% in Lab A and 5.2% in Lab B. Which one is “right?” We don’t know what “right” is because there is no formal standard. However, obtaining the Omega-3 Index from OmegaQuant guarantees you a metric that has been accepted in over 100 research publications over the last 9 years, making it the most published of all the commercially-available methods. A significant advantage of the Omega-3 Index test is the ability to correlate it to clinical outcomes from major epidemiological and interventions studies (see below for “Research behind the test”)

C. The number of fatty acids reported in the profile

In addition to the Omega-3 Index, we also provide, at no additional charge, a complete fatty acid profile including 4 omega-3 fatty acids, 7 omega-6 fatty acids, 4 monounsaturated fatty acids, 6 saturated fatty acids, 3 groups of trans fatty acids, 5 composites (group sums), and 2 ratios (see below). Other ratios or groups of fatty acids can be calculated from these. But beyond these 26 fatty acids, there are still others (very minor components) that can be detected in both RBCs and in whole blood, and some labs will report these as well. It is our view at OmegaQuant that it is possible to provide too much information, and hence we draw the line at these 26, and in many respects, even this is more than can practically be addressed. We provide them as a courtesy to those clients who want to know. Sometimes “less is more” and we believe that applies here. Having said that, we are happy to modify our standard protocol for investigators interested in more obscure fatty acids that are not routinely measured (e.g., odd chain fatty acids).

D. The ratios included in the profile

As noted above, we provide two fatty acid ratios: the omega-6/omega-3 and AA/EPA. Although we include these values, we believe that the Omega-3 Index is, by far, the single most important (and actionable) component of our report. These ratios are provided as a courtesy and because some practitioners find them useful. We would suggest that for the dried blood spot assay, the omega-6/omega-3 ratio that would correspond to an Omega-3 Index of >8% would be 3.5 or less, and for the AA/EPA ratio, the target should be 9 or less. For the red blood cell assay, the target omega-6/omega-3 ratio should be 2.6 or less, and the AA/EPA ratio should be 15 or less.

E. The use of “reference” or “normal” ranges

Included with each the 5 classes of fatty acids are “reference ranges.” The reference range is provided simply to give an idea of how these values compared to a large number of others taken from a relatively healthy population. In the case of the RBC assay, the reference range was taken from approximately 11,000 individuals whose samples were submitted to the laboratory for analysis. In the case of the dried blood spot assay, the reference range was taken from approximately 27,000 individuals. No information regarding the state of health of any of these individuals is known. In both cases, the reference range encompasses 99% of the individuals in their respective populations. Although “average,” these are not necessarily “optimal” levels, i.e., target levels or levels that one should to attempt to achieve. The only result for which we feel justified in providing an actual target or optimal level is the Omega-3 Index since it has undergone the most research. As the research in this area matures, we may recommend new “target” values for other fatty acids or ratios when we believe that they have been adequately validated.

F. The provision of dietary recommendations to correct deviations from “normal”

As noted above, we provide reference ranges for general information only, not to suggest or guide changes in diet. We do not believe that the research has advanced to the point where we can tell people who have a below (or above) “average” level of any given fatty acid class that they should try to change it. There are several reasons for this. First, since most fatty acid levels in the blood are not influenced by diet but are established by internal genetics and metabolism, even attempting to alter a fatty acid level by dietary change would be largely futile. Secondly, we don’t have the data at present to show that even if one could change fatty acid levels (again, except for the Omega-3 Index and trans fatty acids), it would benefit them to do so. So until further research convincingly demonstrates that raising or lowering a certain fatty acid or class is beneficial or not, we will take the conservative approach of simply giving each client the numbers, and they can track them as they wish.

Clearly, we are very comfortable with recommending specific targets for the Omega-3 Index because the research supporting a target of 8% is strong, and we know that you can specifically raise the Index by eating more omega-3. We don’t, however, know exactly how much EPA+DHA any particular person should be told to take to achieve the 8% target. People differ, and so each person’s response to supplemental omega-3s will vary. Just like one cannot predict how much serum cholesterol will go down when a patient is placed on statins, we cannot accurately predict how the Omega-3 Index will respond to an increased intake; it must be individually tested. (See Question 2).

G. The research behind the test

Dr. Harris has been doing research in omega-3s for 30 years, and has over 80 published research papers in this field. In 2004, he, along with his colleague Clemens von Schacky, MD, a cardiologist from Munich, was the first to propose the Omega-3 Index as an independent risk factor for heart disease. More importantly, currently Dr. Harris is the Principal Investigator for and is using the Omega-3 Index test in two major epidemiological studies, both funded by the National Institutes of Health (NIH): the Framingham Heart Study and the Women’s Health Initiative’s Memory Study. In addition, he will be doing the blood analyses in the “VITAL” study which will be testing the effects of omega-3 fatty acid and/or vitamin D on CHD and cancer incidence in 20,000 subjects. Dr. Harris has used the same method in at least 8 additional clinical studies being funded by the NIH.

H. The clinical applicability of the test

Because of the research foundation supporting the Omega-3 Index, its clinical utility will continue to grow and mature as the results of these new studies are published. Health care providers and consumers alike want their results to be comparable to those published in the mainstream medical literature. If high or low risk for disease “X” is defined by a particular Omega-3 Index value as derived from these research studies, then only by using this specific test can you be sure that your level of risk is accurately predicted; a value from another lab may or may not give you a clinically-useful estimate of risk. It is for these reasons that the Cooper Aerobics Center (Dallas, TX) selected OmegaQuant as their sole provider for fatty acid testing.

Yes, we follow Good Laboratory Practices. All of our assays are validated. In particular for plasma/serum total and free (i.e., unbound) concentrations of EPA, DHA, DPA and ARA have been validated per the Guidance for Industry: Bioanalytical Method Evaluation (FDA; May, 2001). These assays (and our red blood cell fatty acid assay) have been and are currently being used in new drug development studies with pharmaceutical sponsors.

Any biological sample that contains fatty acids. Typically we are asked to analyze human plasma or erythrocytes, but we have experience with whole blood, plasma lipid classes (TG, CE, PL, NEFA), lipoproteins (VLDL, LDL, HDL), lipoprotein lipid classes, tissues (biopsies or from animals), tears, fish, and fish oil capsules.

It depends on the sample type, but our typical assays require <25 uL of plasma or blood or RBCs, or about 25 mg of tissues. We prefer to receive aliquots of at least 200 uL for liquid samples. If dried spots are preferred, 25 uL of whole blood or of RBCs mixed 50:50 with Erythrosolve™ (which we will provide) is sufficient. These would be spotted and sent on cards that we have pre-treated with our proprietary anti-oxidant OxyStop®.

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Whole blood, packed RBCs, and dried blood spots are remarkably resistant to degradation and can typically be shipped overnight at ambient temperature. If samples are being collected at a research site for later batch shipment, they should be frozen at -80°C and shipped on dry ice. Note: RBC samples should not be kept at -20°C for more than 1 day as the long-chain PUFAs will begin to degrade. Storage at room temperature or 4°C for up to 3 weeks (before analysis) is acceptable.

[accordion-group title="What analytes and what sample types would be best for my specific research question?"]
This depends on your research question. For example, if a study is examining the short term (1 day to 2-4 weeks) effects of fish oil supplementation on omega-3 status, then plasma is the preferred analytical sample type; if longer term studies are contemplated (>1 month, optimally >4 months), then RBCs provide a more robust picture of status. Platelets turn over in about 10 days, RBCs in 120. Hence, short term studies can use platelets to track fatty acid compositional changes as well as plasma.

Typically in an Excel spreadsheet. See Sample Report on Research menu.

Yes. This is one of the advantages of working with OmegaQuant. Dr. Harris has over 30 years of research experience with fatty acids, and has published >190 papers in this field. He is happy to serve as a coauthor on scientific publications, or to simply provide advice and perspective on the findings for no additional charge.