Monday, April 13, 2009

Common method used for the estimation of LDL cholesterol

Even though the 'Direct Estimation Methods' are more accurate and precise than the conventional methods,(ie Precipitation method for HDL-Cholesterol & Friedewald's formula for LDL-Cholesterol.)the direct methods are not commonly used by clinical laboratories because it is expensive, time consuming, and it requires equipment not commonly available in the clinical lab.

Friedwald’s Formula:It is the conventional method for the estimation of LDL-cholesterol in fasting specimen

The formula

LDL-cholesterol = Total cholesterol - HDL cholesterol - VLDL

VLDL=TRIGLYCERIDES /5


Limitation of Friedwald's formula

Friedewald formula is unreliable in the presence of chylomicronemia ,hypertriglyceridemia (when plasma triglyceride concentration exceeds 400 mg/dL or 4.52 mmol/L) and in patients with dysbetalipoproteinemia (type III hyperlipoproteinemia).

Further reading

http://www.clinchem.org/cgi/content/full/43/11/2183

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