Comparison Between the Direct Method and Friedewald's Formula for the Determination of Low-Density Lipoprotein Cholesterol Serum Levels in Horses.

This study aimed to compare the use of enzymatic colorimetry and Friedewald's formula for the determination of LDL in horses. A total of 260 samples were used. Direct analysis was performed to determine low-density lipoprotein (LDL), high-density lipoprotein (HDL) cholesterol, triglycerides (TG), and total cholesterol (TC). The LDL level was calculated using the Friedewald equation (LDL= TC-HDL-TG/5). The correlations between the direct LDL analysis and the LDL calculated using the Friedewald formula were determined by Pearson's tests, and the coefficient of determination was also obtained by linear regression using SAS software (P<.05) and the kappa value. The mean value (± standard deviation) of the LDL was 22.12 (±10.34) mg/dL, and that of the result obtained by the Friedewald formula was 19.94 (±19.13) mg/dL. The correlation between the two variants analyzed in this experiment was significant, with a value of P < .001, and values of r = 0.688 and R = 0.4893. These results are relevant, given that recent studies have demonstrated a correlation between LDL plasma values and equine metabolic syndrome. Previous studies have reported discrepancies between the data obtained using Friedewald's method and the LDL-c values directly determined in humans and animals. The results of the present study suggest that the Friedewald method can be used to estimate the LDL plasma concentration in horses. Nevertheless, the coefficient of determination was not found to be adequate to recommend the Friedewald formula as a replacement for the enzymatic colorimetric method in determining LDL in horses.