Correlations between Direct and Calculated Low-Density Lipoprotein Cholesterol Measurements in Children and Adolescents.

Background Low-density lipoprotein cholesterol (LDL-C), as a modifiable risk factor for atherosclerotic cardiovascular disease, should be assessed and monitored. This study compared directly measured and Friedewald-estimated LDL-C values in children and adolescents. Methods Blood samples were collected from 464 children and adolescents. Calculated LDL-C (CLDL-C) levels were estimated using the Friedewald formula for any triglyceride value below 4.6 mmol/L. Direct LDL-C (DLDL-C) levels were measured on an ARCHITECT c8000 Abbott Clinical Chemistry Analyzer. The differences in LDL-C were then calculated. Results The correlation coefficients (R) between DLDL-C and CLDL-C were 0.978 (P = .148) and R = 0.970 (P = .052) for children and adolescents, respectively. Children with LDL-C values above 4.92 mmol/L had a correlation value of 0.971 (P = .419). The correlation and agreement between DLDL-C and CLDL-C in adolescents were moderate for LDL-C below 2.85 mmol/L (R = 0.806; 84.1%) and improved above 2.85 mmol/L (R = 0.978; 91.5%). In children, good correlations between DLDL-C and CLDL-C were observed for normal (<0.85 mmol/L), borderline (0.85-1.12 mmol/L), and abnormal (>= 1.13 mmol/L) triglyceride levels (R = 0.9782, 0.990, and 0.951, respectively). The rates of agreement were better for normal (80.5%) and borderline (82.9%) but not abnormal (68.2%) triglyceride levels. Conclusion We observed good agreement between DLDL-C and CLDL-C in both children and adolescents. The Friedewald formula provided an adequate estimate of LDL-C for most fasting specimens. LDL-C difference percentage can also be used as a quality indicator to check laboratory analyzer performance in healthy subjects.