The Friedewald formula for the calculation of low-density lipoprotein cholesterol (LDL-C) values is fairly accurate provided the triglyceride value is less than 400 mg/dL. It is not clear whether the estimation is also valid in the presence of low triglyceride and high cholesterol levels. We describe herein a patient with a low triglyceride value of approximately 50 mg/dL, a high cholesterol level, and a discrepant LDL-C level. The LDL-C level using the Friedewald calculation turned out to be much higher than the LDL-C level using direct measurement. We, therefore, suggest that in the presence of low triglyceride and high cholesterol levels, the LDL-C level should be measured directly instead of using the Friedewald calculation.
The impact of low serum triglyceride on LDL-cholesterol estimation. Excerpt:
Carbohydrate restriction favorably alters lipoprotein metabolism in Emirati subjects classified with the metabolic syndrome . Abstract conclusion:
Statistical analysis showed that when triglyceride is <100 mg/dL, calculated low- density lipoprotein cholesterol is significantly overestimated (average :12.17 mg/dL or 0.31 mmol/L), where as when triglyceride is between 150 and 300 mg/dL no significant difference between calculated and measured low-density lipoprotein cholesterol is observed. In patients with low serum triglyceride and undesirably high total cholesterol levels, Friedewald equation may overestimate low-density lipoprotein cholesterol concentration and it should be either directly assayed or be calculated by a modified Friedewald equation.
These results suggest that weight loss favorably affects lipoprotein metabolism and that the CRD [carbohydrate restricted diet] had a better effect on atherogenic [deposits leading to atherosclerosis contained in] VLDL and HDL than the low fat diet recommended by AHA.