title: Reliability of Calculated Low-Density Lipoprotein Cholesterol.
abstract: Aggressive low-density lipoprotein cholesterol (LDL-C)-lowering strategies are recommended for prevention of cardiovascular events in high-risk populations. Guidelines recommend a 30% to 50% reduction in at-risk patients even when LDL-C concentrations are between 70 and 130 mg/dl (1.8 to 3.4 mmol/L). However, calculation of LDL-C by the Friedewald equation is the primary laboratory method for routine LDL-C measurement. We compared the accuracy and reproducibility of calculated LDL-C <130 mg/dl (3.4 mmol/L) to LDL-C measured by β quantification (considered the gold standard method) in 15,917 patients with fasting triglyceride concentrations <400 mg/dl (4.5 mmol/L). Both variation and bias of calculated LDL-C increased at lower values of measured LDL-C. The 95% confidence intervals for a calculated LDL-C of 70 mg/dl (1.8 mmol/L) and 30 mg/dl (0.8 mmol/L) were 60 to 86 mg/dl (1.6 to 2.2 mmol/L) and 24 to 60 mg/dl (0.6 to 1.6 mmol/L), respectively. Previous recommendations have emphasized the requirement for a fasting sample with triglycerides <400 mg/dl (4.5 mmol/L) to calculate LDL-C by the Friedewald equation. However, no recommendations have addressed the appropriate lower reportable limit for calculated LDL-C. In conclusion, calculated LDL-C <30 mg/dl (0.8 mmol/L) should not be reported because of significant deviation from the gold standard measured LDL-C results, and caution is advised when using calculated LDL-CF values <70 mg/dl (1.8 mmol/L) to make treatment decisions.
authors.affiliation: Division of Clinical Core Laboratory Services, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota. Electronic address: meeusen.jeffrey@mayo.edu.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Meeusen
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic Arizona, Scottsdale, Arizona.
authors.forename: Christine L
authors.initials: CL
authors.lastname: Snozek
authors.affiliation: Division of Clinical Core Laboratory Services, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Nikola A
authors.initials: NA
authors.lastname: Baumann
authors.affiliation: Division of Clinical Core Laboratory Services, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota; Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, Minnesota.
authors.forename: Allan S
authors.initials: AS
authors.lastname: Jaffe
authors.affiliation: Division of Clinical Core Laboratory Services, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota.
authors.forename: Amy K
authors.initials: AK
authors.lastname: Saenger
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood*; D015331:Cohort Studies; D005215:Fasting / Q000097:blood; D005260:Female; D006801:Humans; D006937:Hypercholesterolemia / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D014280:Triglycerides / Q000097:blood
chemical_list: D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D014280:Triglycerides