Letter to editor
A practical method to determine the “atherogenic lipoprotein phenotype”

Increasing evidence suggests that the “quality” rather than only the “quantity” of low density lipoproteins (LDL) exerts a great influence on cardiovascular risk [1]. Higher plasma triglyceride levels and decreased HDL cholesterol concentrations are usually accompanied by the presence of small, dense LDL in the so-called “atherogenic lipoprotein phenotype” (ALP) or lipid triad [1]. This phenotype is highly atherogenic and its prevalence may suggest higher overall burden of atherosclerotic disease than that associated with hypercholesterolaemia. As stated by the National Cholesterol Education Program Adult Treatment Panel III [2], there is evidence that each component of the lipid triad is individually atherogenic but the relative contribution of each component cannot be easily determined. For this reason, it has been suggested to consider this trait as a whole as a “risk factor”. This is supported by data from epidemiological studies considering high-risk populations, which showed that the contribution to cardiovascular risk of each individual component of atherogenic dyslipidaemia cannot be dissected from the sum of all lipid risk factors [2]. Yet, treatment plans have not suggested so far how to exactly measure ALP in clinical practice. For this reason, several and contrasting criteria have been followed to assess ALP; for instance, regarding triglycerides it has been suggested to consider the highest quartile [3] or concentrations >75th or >90th percentile according to age and gender [4], as well as levels >1.5 mmol/l [5]. Regarding HDL cholesterol it has been proposed to consider the lowest quartile [3] or concentrations <25th percentile according to age and gender [4], as well as levels <1.1 mmol/l [5]. The predominance of small, dense LDL has been measured by levels of LDL3 subclass (density 1.044-1.060 kg/l) >40% of total LDL particles, as isolated by density gradient ultracentrifugation [5], or by apolipoprotein B concentrations in LDL5+LDL6 subclasses >25 mg/dl, as isolated by density gradient ultracentrifugation too [6]. We propose here a practical method to calculate ALP in whole plasma. According to the National Cholesterol Education Program Adult Treatment Panel III [3], and as confirmed by the recent guidelines of the joint American Heart Association/National Heart, Lung, and Blood Institute on “Diagnosis and management of the metabolic syndrome”, we considered low HDL cholesterol...


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