Marked effects of extreme levels of lipoprotein(a) on estimation of low-density lipoprotein cholesterol

Abstract Background Low-density lipoprotein cholesterol (LDL-C) is usually calculated using the Friedewald equation. However, this calculation method does not account for the cholesterol associated with lipoprotein(a) [Lp(a)]. Using the Dahlen equation, Li et al. have shown a strong positive correlation between serum Lp(a) levels and overestimation of LDL-C levels. Objective To determine how the extreme levels of Lp(a) influence the LDL-C calculation. Methods We performed a retrospective chart review of the lipid profile and Lp(a) of 223 patients (men and women). LDL-C was calculated using the Friedewald equation. Lp(a) concentrations were measured by an ELISA. Other serum lipids were measured enzymatically by standard methodology. Corrected LDL-C was calculated using the Dahlen equation. Results We found that this overestimation is very significant in individuals with extreme levels of Lp(a) (mean overestimation of 40% at Lp(a) > 1200 mg/L). Conclusions Calculated LDL-C is markedly overestimated in patients with extreme levels of Lp(a).