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.