Is directly measured low-density lipoprotein clinically equivalent to calculated low-density lipoprotein?

• Published in: Journal of clinical lipidology 2010-07, Vol.4 (4), p.259-264
• Main Authors: Baruch, Lawrence, MD, Agarwal, Sanjay, MD, Gupta, Bhanu, MD, Haynos, Ann, BA, Johnson, Swapna, MD, Kelly-Johnson, Katelyn, BS, Eng, Calvin, MD
• Format: Article
• Language: English
• Subjects: Aged; Anticholesteremic Agents - therapeutic use; Blood Chemical Analysis - methods; Cardiovascular; Cholesterol - blood; Cholesterol, LDL - blood; Female; Health policy; Humans; Hypercholesterolemia; Hypertriglyceridemia - drug therapy; LDL-C cholesterol; Lipids; Lipoproteins, HDL - blood; Lipoproteins, LDL - blood; Male; Middle Aged; Therapeutic Equivalency; Triglycerides - blood
• ISSN: 1933-2874; 1876-4789
• DOI: 10.1016/j.jacl.2010.05.003

Background Low-density lipoprotein cholesterol (LDL-C) can either be calculated or measured directly. Clinical guidelines recommend the use of calculated LDL-C (C-LDL-C) to guide therapy because the evidence base for cholesterol management is derived almost exclusively from trials that use C-LDL-C, with direct measurement of LDL-C (D-LDL-C) being reserved for those patients who are nonfasting or with significant hypertriglyceridemia. Objective Our aim was to determine the clinical equivalence of directly measured-LDL-C, using a Siemens Advia Chemistry System, and fasting C-LDL-C. Methods Eighty-one subjects recruited for two cholesterol treatment studies had at least one C-LDL-C and D-LDL-C performed simultaneously; 64 had a repeat lipid assessment after 4 to 6 weeks of therapy, resulting in 145 pairs of C-LDL-C and D-LDL-C. Results There was significant correlation between D-LDL-C and C-LDL-C (r2 = 0.86). Correlation was significantly better in those with lower total cholesterol, triglycerides, and high-density lipoprotein. In 60% of subjects, the difference between D-LDL-C and C-LDL-C was more than 5 mg/dL and greater than 6%. Clinical concordance between D-LDL-C and C-LDL-C was present in 40% of patients, whereas clinical discordance was noted in 25%. One-third had greater than a 15 mg/dL difference between D-LDL-C and C-LDL-C, whereas 25% had a greater than 20 mg/dL difference. In 47% of subjects, the difference between D-LDL-C and C-LDL-C at baseline and follow-up changed by a minimum of 10% or 10 mg/dL. Conclusions Our findings suggest that D-LDL-C is not clinically equivalent to C-LDL-C. This puts into question the current recommendation of using D-LDL-C in situations in which C-LDL-C would be inaccurate.