STABILITY OF RED-BLOOD-CELL MEMBRANE FATTY-ACID COMPOSITION AFTER ACUTE MYOCARDIAL-INFARCTION

Questionnaire-based assessment of dietary intake may be invalidated in case-control studies by biases of recall, reporting or interviewing. Biomarkers, free of such biases, can be useful adjunct measures if the y themselves are not affected by the event under investigation. Conseq uently, we studied the stability of the fatty acid composition of the red blood cell (RBC) membrane during a 1-week period, in 20 patients a ged 40-74 years after an acute myocardial infarction (MI). Statistical analysis that accounted for a repeated measures design with missing d ata was undertaken for five fatty acids: C16:0, C18:1, C18:2, C20:5 an d C22:6. All fatty acids showed change over the 7 day period. Individu als tended to maintain their relative ranking over time as reflected b y correlations between time points of between 0.85 to 0.90, with the e xception of C16:0 in which correlations were lower and inconsistent. O ver the first 24 hr from admission all fatty acids except C20:5 showed evidence of a statistically significant change. However over the firs t 7 hr C18:1, C18:2, C20:5 and C22:6 exhibited stability whereas C16:0 altered. We conclude that the fatty acid composition of the RBC membr ane appears to change soon after an acute MI. Consequently, case-contr ol studies may be biased towards positive associations for C16:0 and i nverse associations for C18:2 and C20:5, i.e. consistent with conventi onal predictions. However, if blood samples are drawn within 6 hr of a dmission, bias in estimation of C18:1, C18:2, C20:5 and C22:6 may be u nimportant.