The unreliability of the Friedewald-calculated LDL-C levels rises at lower levels of LDL-C, par- ticularly <70 mg/dL (<1.8 mmol/L). If accurate measurements of LDL-C levels are needed at very low LDL-C, calculation adjustments can be Measurement of apoB may be use- ful in determining whether hypertriglyceridemia is an atherogenic condition.S2.2-12,S2.2-13 4. In adults with a family history of premature ASCVD or genetic hyperlipidemia, a fasting lipid profile is reasonable for initial evaluation to aid in the understanding and identification of familial 2.3. Measurements of Apolipoprotein B and Lipoprotein (a) Two lipoprotein entities related to LDL-C are apoB and lipoprotein (a) [Lp(a)]. Because apoB is the major apoli- poprotein embedded in LDL and VLDL, several investiga- tors identify strength of association between apoB and Others report a high correlation between apoB and non HDL-C.S2.3-2 Under certain circumstanc- es, particularly in patients with hypertriglyceridemia, the measurement of apoB may have advantages.S2.3-3 Nevertheless, apoB measurement carries extra expense, and its measurement in some laboratories may not be A relative indication for its measurement would be triglyceride 200 mg/dL. A level >130 mg/dL corresponds to an LDL-C level 160 mg/dL and consti- tutes a risk-enhancing factor. A persistent elevation of apoB can be considered a risk-enhancing factor. Sepa- rately, Lp(a) is a modified form of LDL that appears to possess atherogenic potential.S2.3-5 Relative indications for its measurement are family history of premature ASCVD or personal history of ASCVD not explained by major risk factors. Lp(a) increases ASCVD risk especially at higher levels. 