Discordance analyses comparing LDL cholesterol, Non-HDL cholesterol, and apolipoprotein B for cardiovascular risk estimation

For decades, studies have tried to identify the cholesterol marker that best reflects risk of atherosclerotic cardiovascular disease(ASCVD). Comparing low-density-lipoprotein(LDL) cholesterol, non-high-density-lipoprotein(non-HDL) cholesterol, and apolipoprotein B(apoB) as ASCVD risk markers has been challenged by high correlation between them. Thus, discordance analyses, directly addressing disagreements between the cholesterol markers, have emerged. Approaches adopted to define discordance originate in one of three methods: discordance by cut-points, discordance by percentiles, or discordance by residuals. Commonly, concordant lipid levels serve as reference examining the association between discordant lipid levels with risk of ASCVD. Importantly, concordant reference groups present heterogeneity of clinical relevance across different discordance methods as concordant low lipid levels associate with lowest ASCVD risk while concordant high lipid levels associate with highest risk. Thus, results from different discordance approaches cannot be directly compared. Moreover, discordance between cholesterol markers is more frequently seen in individuals treated with lipid-lowering medication than in individuals not treated with lipid-lowering medication. Accordingly, studies performing discordance analyses have reported inconsistent and even conflicting results. Discordance by cut-points appears the most intuitive and clinically applicable method; results from these analyses suggest that elevated LDL cholesterol, non-HDL cholesterol, or apoB levels in individuals not treated with lipid-lowering medication confer increased ASCVD risk while in individuals treated with lipid-lowering medication, elevated non-HDL cholesterol and apoB levels best indicate residual risk. Results from discordance analyses comparing LDL cholesterol, non-HDL cholesterol, and apoB in risk of ASCVD as well as complexities of discordance analyses and considerations regarding interpretations are discussed in this review.