Impact of Analytical Error in Lipid Levels and LDL-c Calculation on Cardiovascular Risk Classification

Introduction: High levels of low-density lipoprotein cholesterol (LDL-c) are associated with a high risk of cardiovascular disease (CVD). The LDL-c value is the basis for a classification of the subject into low risk, moderate risk, and very high risk of developing CVD. Nevertheless, analytical error could be reflected in the various calculation parameters. The aim of this study was to determine the influence of analytical error and the method of LDL- c calculation on patient classification. Materials and Methods: This was a retrospective study with data collection on lipid panels carried out in the laboratories of three hospitals in Gabon, between January 2023 and December 2023. Each data set included concentrations of total cholesterol (TC), HDL-c, LDL-c, and triglycerides (TG) measured simultaneously for each patient. Not included were all patients with TG >4 mmol/L. The LDL-c concentration was determined using the direct method and Friedewald equation. The total analytical error (TAE) used are for TC ≤ 9%, TG ≤ 15%, LDL-c ≤ 12%, and HDL-c ≤ 13%. Results: A total of 2060 patients made up the study population. Before application of the TAE, the proportion of LDL-c concentration with the direct method against the Friedewald equation was comparable (p=0.14). After application of the positive TAE, the proportion of LDL-c concentration was statistically higher with the indirect method compared to direct method [596 (28.93%) versus 355 (17.23%); p<0.0001]. Thus, applying the positive TAE to the calculation formula and to the direct LDL-c, the Friedewald equation had more patients at very high risk and at high risk compared to the direct method (p<0.0001). However, the negative TAE on the indirect method classified few patients at very high risk and at high risk. We found that, the positive TAE reduced patients at low and intermediate risk and reclassified them at very high and at high risk of developing CVD (p<0.0001). Conclusion: The analytical error and LDL-c calculation method significantly influence patient classification. It revealed that high-risk patients were more likely to be classified as CVD-related. The use of indirect methods led to higher high- and very high-risk patients. The TAE also altered patient classification, shifting some from lower to higher risk. This suggests that TAE should be considered for better patient management.