<prompt> Find out the value of LDL, if total cholesterol level is 300 mgdL, HDL level is 25 mgdL and triglycerides level is 150 mgdL:5595125245  <response>: Ans. d. 245 Ref :Harrison 19e p2446; Clinical Laboratory Medicine by Kenne 2e p3I9Plasma lipid and lipoprotein levels should be measured in all adults, preferably after a 12-h overnight fast. In most clinical laboratories, the total cholesterol and TGs in the plasma are measured enzymatically, and then the cholesterol in the supernatant is measured after precipitation of apoB-containing lipoproteins to determine the HDL-C. The LDL-C is then estimated using the following equation: LDL-C total cholesterol -- TG5-HDL-C The VLDL cholesterol content is estimated by dividing the plasma TG by 5, reflecting the ratio of TG to cholesterol in VLDL particles. This formula the Friedewald formula is reasonably accurate if test results are obtained on fasting plasma and if the TG level does not exceed 200 mgdL; by convention it cannot be used if the TG level is 400 mgdL. --Harrison 19e p2446Friedewald EquationThe ultra centrifugal measurement of LDL is time consuming expensive and require specialist equipment.For this reason, LDL-cholesterol is most commonly estimated from quantitative measurements of total and HDL-chntesterol and plasma triglycerides using the empirical relationship of Friedewald et al.Total cholesterol LDL HDL Triglycerides5Total cholesterol LDL HDL Triglycerides5300 LDL 25 1505LDL 300 - 25 30 245 mgdlLimitations of Friedewald EquationFriedewald Equation should not be used under the following circumstances:When chylomicrons are presentWhen plasma triglyceride concentration exceeds 400 mgdLIn patients with dysbeta-lipoproteinemia type III hyperlipoprteinemia 