The expression of results of lipid determinations in arterial tissues: mass per unit weight vs mass per unit area

The interrelations among four methods of expressing the results of lipid determinations in the intima of the abdominal aorta were examined using rank order and product moment correlation methods. The rank order correlations among the four methods were all uniformly high (0.90 or better), indicating that the method of expressing results of lipid analyses is not important when ranking by amount of lipid is the object. The product moment correlations showed a pattern of strong association when the methods paired are expressions of either "content" (mg lipid per 1/2 abdominal aorta vs mg lipid per unit area of aorta, r = 0.980) or "concentration" (mg lipid per dry weight of tissue vs mg lipid per dry defatted weight of tissue, r = 0.980). Correlations of paired methods that express "content" and "concentration" were lower and share only about 50% of common variability. This result can be interpreted as evidence that it is worthwhile to consider reporting chemical findings in reference to units of intimal (or artery) area as well as to unit of weight. If both methods are used some of the problems in interpreting chemical findings in the arterial wall may be clarified.