APOA1 and systemic lupus erythematosus: While these are mainly descriptive studies, where HDL-C concentrations are used as a proxy of HDL levels, emerging approaches are trying to investigate other parameters that could better mark the number of HDL particles, including NMR analysis [11,12] or the measurement of the key structural protein of HDL, namely, apoA-I, whose levels are also decreased in patients with SLE [13].