Utility of Discrepancies Between Friedewald and Martin Equations in Predicting Pathogenic Variants of Familial Hypercholesterolemia in Children.

Background: The Friedewald equation, commonly used to calculate low-density lipoprotein cholesterol (LDL-C), occasionally yields inaccurate estimations for very-low-density lipoprotein cholesterol, suggesting the need for an alternative method such as the Martin equation. In this study, we aimed to evaluate the discrepancies between the Friedewald and Martin equations, particularly in the context of pathogenic variants associated with familial hypercholesterolemia (FH).

Methods and results: We evaluated the discrepancies between LDL-C levels calculated using the Friedewald and Martin equations, and for the presence of pathogenic variants of FH in 53 children with hypercholesterolemia detected through universal lipid screening. Genetic testing revealed pathogenic variants of FH in 24 of the 53 children. Chi-squared tests indicated a significant difference in the presence of pathogenic variants of FH between the "Friedewald ≥ Martin" and "Friedewald < Martin" groups (χ²=11.348, P<0.001). Even in 37 children with LDL-C <180 mg/dL, discrepancies between the equations were still associated with the presence of pathogenic FH variants (Fisher's exact test, P=0.028).

Conclusions: Discrepancies in LDL-C levels measured by the Friedewald and Martin equations might serve as a useful predictive marker for identifying pathogenic variants of FH, especially in cases of LDL-C <180 mg/dL, which are often challenging to diagnose.