Background:
Low-density lipoprotein cholesterol(LDL-C) in serum is one of the important risk factors in coronary heart disease and is calculated by the Friedewald formula in the clinical laboratory. But the calculated LDL-C does not account for the
cholesterol
associated with lipoprotein(a)[Lp(a)]. The purpose of this study was to investigate the effect of serum Lp(a) on estimation of LDL-C by the Firedewald formula.
Methods:
We measured the lipid profiles on 496 specimens containing less than 400 mg/dL of triglyceride. The concentrations of LDL-C were compared among 3 groups of serum specimens that contained normal(≤20 mg/dL), intermediate(20-50 mg/dL) and
high(>50
mg/dL) levels of serum Lp(a) , respectively. A correction coefficient was determined that would eliminate the effect of serum Lp(a), respectively. A correction coefficient was determined that would eliminate the effect of serum Lp(a) on the
calculation
of LDL-C by the Friedewald formula.
Results:
The mean concentrations and standard deviations of calculated LDL-C were 108.5±35.9 mg/dL, 119.0±34.3 mg/dL and 126.4±40.6 mg/dL for sera with normal, intermediate, and high levels of Lp(a), respectively. The differences in the calculated
LDL-C
concentrations between the high group and the normal or intermediate group were highly significant(p=0.0052, 0.0002). These differences were eliminated when three tenth of the concentration of Lp(a) was subtracted from the calculated amount of
LDL-C
according to the Friedewald formula. The concetrations of the corrected LDL-C in the 3 group of sera were 106.1±35.6 mg/dL, 108.7±34.1 mg/dL , and 105.8±40.9 mg/dL, respectively
Conclusions:
The Fridewald formula may be modified to take into consideration the effect of Lp(a) cholesterol.
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