Translating plasma eicosapentaenoic acid concentrations into erythrocyte percentages of eicosapentaenoic acid plus docosahexaenoic acid during treatment with icosapent ethyl.
Level 4 - case-series / case-control
Cross-sectional modeling and mathematical estimation using retrospective laboratory data
PubMed 31401072 · doi:10.1016/j.jacl.2019.07.001
What was done
Researchers generated a linear regression equation using deidentified laboratory data from 2,311 patients with lipid profiles similar to the REDUCE-IT trial population to model the relationship between plasma fatty acids and erythrocyte Omega-3 Index (RBC EPA plus DHA percentage). This equation, along with previously published RBC fatty acid data, was used to mathematically estimate baseline and post-treatment Omega-3 Index values in REDUCE-IT participants receiving 4 g/day of icosapent ethyl.
What was found
Both mathematical modeling and conversion of prior published trial data estimated baseline Omega-3 Index levels at approximately 5% and on-treatment levels at approximately 7% after 4 g/day icosapent ethyl. Additionally, plasma EPA levels were found to be influenced by triglyceride levels, whereas the erythrocyte Omega-3 Index was not.
Why it matters
This study provides an estimated target erythrocyte Omega-3 Index of approximately 7% corresponding to the cardioprotective benefits seen in REDUCE-IT, while indicating that plasma EPA measurements are confounded by circulating triglycerides.
Limits
The study did not directly measure erythrocyte fatty acids in the REDUCE-IT cohort; findings rely entirely on mathematical modeling and proxy laboratory data. Precision and confidence intervals for the estimations were not reported in the abstract.
Cited by
- supports Typical normal plasma EPA and DHA level is around 2% of total fatty acids, compared to around 5% to 6% in red blood cell membranes.