Abstract

Introduction: The aim of the current study was to investigate the impact of low serum triglyceride (TG) on LDL-cholestrol estimation by Friedewald formula. Methods: Serum samples were taken from 540 patients and divided into 4 groups based on the level of the TG 100>, 100-150, 150-250 and 250-400 mg/dl. The total cholestrol (TC), TG, high density lipoprotein (HDL) and low density lipoprotein (LDL) were measured. Then, the LDL of patients whose serum levels of TG>400 was measured with the direct method and calculated as follows: Friedewald method= LDL - C (mg/dl) = TC-TG/5 - HDL. The results of Friedewald formula compared with the direct measurement results. Findings: According to the results, a significant difference observed between Cholesterol (LDL-C) measured by the direct method than Friedewald equation in patients with TG>400 levels (P<0.001). No significant differences were observed in patients with TG 250-400 levels (P>0.05). A correlation reported between LDL-C measured by the direct and Friedewald Equation methods (P<0.001). Conclusion: These results suggested there was higher difference of LDL-C in low TG levels (100> and 100-150 mg/dl) measured by direct method and Friedewald Equation formula. Negligible differences observed in high TG levels (150-250 and 250-400 mg/dl) using direct method and Friedewald Equation formula. With increased TG levels (up to 400mg/dl), the overestimation of the LDL-C level is decreased by Friedewald formula. So, in high TG levels, Friedewald Equation formula is reliable.