Low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol and apolipoprotein B: relationships among the different measurements.
Serum low-density lipoprotein cholesterol (LDLC) value is a recognized target for atherosclerotic risk management, and is generally calculated using the "Friedewald formula". Alternative risk markers include directly measured LDLC, non-high-density lipoprotein cholesterol (non-HDLC) and apolipoprotein B (ApoB). The relationships among such various measured or calculated quantities in medium-sized sets of patient results were investigated. Results from two sets of patients were retrieved from our laboratory information systems. One group (n=8436) included results of cholesterol, HDLC, triglyceride (TG) and glucose measurements. A second group (n = 902) included, in addition, results of ApoB measurement. The results confirmed the unreliability of the Friedewald formula at TG >350 mg/dL (3.96 mmol/L), but also indicated TG-linked underestimation of LDLC below such a TG level. By contrast, non-HDLC values were shown to be independent of TG, and better correlated to ApoB than LDLC values. Mathematically, the difference between non-HDLC and LDLC is TG x 0.458 (values in mmol/L): therefore, the latter cannot be compared to (or converted into) the former by simply adding a constant amount. The ratio LDLC/ApoB was shown continuously to decrease with increasing TG concentrations, while the ratio non-HDLC/ApoB did not. The TG-dependent underestimation of LDLC may be the reason for the reported better cardiovascular risk predictivity of non-HDLC in diseases associated with TG increase, such as in diabetes. Non-HDLC values are not influenced by TG levels, and are better correlated with ApoB.
Franzini
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Dipartimento di Scienze Cliniche Luigi Sacco, Università degli Studi di Milano, Milan, Italy. carlo.franzini@unimi.it
Valente
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Luraschi
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D001055:Apolipoproteins B / Q000097:blood*; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood*; D006801:Humans
D001055:Apolipoproteins B; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL