Low triglyceride levels affect calculation of low-density lipoprotein cholesterol values

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.