Comparison of lipid fatty acids on a concentration basis vs weight percentage basis in patients with and without coronary artery disease or diabetes.

Lipid fatty acid compositions are almost always expressed on a weight percentage basis rather than as weight or molar concentrations. With the former method of calculation, each fatty acid has an effect on the composition of the other fatty acids, an interdependence that can potentially lead to inaccurate and misleading results. Here we compare the concentrations per liter and the weight percentage compositions of cholesteryl ester and phospholipid fatty acids in individuals with and without coronary artery disease as well as free fatty acid compositions in individuals with and without diabetes. A new method for quantifying lipid fatty acids is also presented. Fatty acid results expressed as concentrations and those calculated on a weight percentage basis may lead to different conclusions, because significant differences between patient groups can be lost with the latter approach. We conclude that serum concentrations of lipid fatty acids are more accurate reflections of changes in lipid fatty acids than are weight percentage calculations, and are more easily interpreted in metabolic and therapeutic terms.

Studies of the accuracy of measurements of serum high density lipoprotein cholesterol levels.

Titration of serum lipoproteins with three different precipitants--heparin-MnCl2 92 mmol.L-1, dextran sulfate-MgSO4, and phosphotungstate-MgCl2--revealed gross errors in the high density lipoprotein cholesterol (HDL-C) levels measured in some hyperlipidemic sera. Dilution studies of eight normal sera with the phosphotungstate method revealed that the most reliable estimate of the HDL-C level was the level measured in the least diluted aliquot that yielded a good precipitate. With a heparin-MnCl2 kit, serial dilution of a lipemic serum demonstrated a requirement for a blank correction. Establishing an accurate estimate of the HDL-C level sometimes requires knowledge of the titration curve of the lipoprotein precipitant being used, a blank correction, and data obtained from dilution studies (or studies with increased precipitant levels) on the serum in question.

Serum cholesterol levels in selected air force cadets compared with levels in the West Point study.

In the USAFSAM Cardiovascular Disease Followup Study, the surprising rise in average cholesterol levels in West Point cadets during the 6 years following their entry into the U.S. Military Academy in 1952 implied a significant increase in risk of heart disease in later years. To ascertain whether that pattern of change suggested increased risk is characteristic of cadets at military academies, a similar study on a smaller scale was conducted on U.S. Air Force Academy cadets beginning in 1972. Randomly selected cadets were monitored throughout their 4-year training at the U.S. Air Force Academy. Mean levels of serum cholesterol were similar at the beginning and end of the study; values between those times were generally somewhat lower. Average body fat never exceeded 12.6%; the average remained close to 12% during the last 3 years. Possible reasons for the differences between the pattern of change in serum cholesterol in the West Point cadets in earlier years (1952-56) and in the U.S. Air Force Academy cadets are discussed. Differences in exercise or stress levels were ruled out as likely explanations. Changes in dietary fat intakes may account for the differences, while unidentified changes in the social environment are possible contributory factors.