Evaluation of alternative calculation methods for determining LDL cholesterol.
BACKGROUND
Due to limitations of the Friedewald formula, alternative methods for calculating low-density lipoprotein cholesterol (LDL-C) were suggested. We evaluated utility of these methods.


METHODS
Ninety three subjects free of coronary heart disease were considered. LDL-C was measured by the homogeneous method, and calculated by the Friedewald formula LDL-C = TC-HDL-(TG/2.2) (LDL1) and alternative formulas LDL-C = 0.41 TC - 0.32 TG + 1.70 apoB - 0.27 (LDL2) and LDL-C = 0.94 TC - 0.94 HDL - 0.435 TG (LDL3).


RESULTS
All three formulas underestimated the measured LDL-C, both in the whole group and in subgroups according to TG levels (TG < 1.7 and in a range of 1.7-4.5 mmol/l, p < 0.001 for all). We found significantly higher bias for all three formulas in subjects with 1.7 < or = TG < 4.5 mmol/l levels. The Friedewald formula showed the lowest assay bias in all the groups investigated. The mean absolute bias for LDL1 was 7.6%, 18.3% for LDL2 and 13.6% for LDL3, respectively. Linear regression analysis showed correlation of calculated LDL-C values with the direct method in the range of r = 0.82 - 0.90 (p < 0.0001 for all, except of LDL2 in 1.7 < or = TG < 4.5 mmol/l group where p = 0.0011).


CONCLUSIONS
The Friedewald formula seems to be a better estimator of LDL-C in our study than the other two alternative formulas; however, it underestimated the LDL-C levels.
Vohnout
B
B
2nd Dept. of Internal Medicine, School of Medicine, Comenius University, Bratislava, Slovakia. branislav.vohnout@rm.unicatt.it
Vachulová
A
A
Blazícek
P
P
Dukát
A
A
Fodor
G
G
Lietava
J
J
D000328:Adult; D008078:Cholesterol, LDL / Q000097:blood*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011933:Reagent Kits, Diagnostic; D014280:Triglycerides / Q000097:blood
D008078:Cholesterol, LDL; D011933:Reagent Kits, Diagnostic; D014280:Triglycerides