Concordance between LDL-C estimated by various formulas and directly measured LDL-C.

BACKGROUND

Although direct measurement of low-density lipoprotein cholesterol (LDL-C) in blood is possible, there are several formulas for its estimation. The performance and concordance of these formulas have not been evaluated in Colombia.

OBJECTIVE

To determine the concordance between LDL-C directly measured using the enzymatic technique and existing methods to calculate it.

METHODS

Study of diagnostic tests, and concordance. We analyzed complete lipid profile samples, which included direct measurement of LDL-C, from 2014 to 2022 at Hospital Universitario San Ignacio (Bogotá, Colombia). The direct LDL-C measurements were compared with estimations using the DeLong, Sampson, Friedewald, extended Martin/Hopkins, Anandaraja, and Cordova methods. Lin's concordance correlation coefficient (CCC) and Bland-Altman plots were employed, conducting subgroup analyses based on triglycerides (TG), and LDL-C levels. Kappa coefficients assessed agreement in LDL-C risk categories according to dyslipidemia guidelines.

RESULTS

A total of 2144 samples were evaluated. The formulas with the best CCC were DeLong (0.971) and Sampson (0.969), with no relevant differences. The extended Martin/Hopkins formula (0.964) and the Friedewald formula (0.964) also performed well. The Anandaraja (0.921) and Cordova (0.881) equations exhibited inferior performance. For all formulas, a decrease in concordance was observed when TG were ≥ 400 mg/dL or when LDL-C was <100 mg/dL. Most formulas demonstrated optimal agreement when assessed using risk categories according to dyslipidemia guidelines, except for Anandaraja and Cordova.

CONCLUSIONS

The DeLong, Sampson, extended Martin/Hopkins, and Friedewald formulas show the best concordance with directly measured LDL-C, so in most cases the results can be considered interchangeable. However, the Anandaraja and Cordova formulas are not recommended.