Vnitr Lek 2008, 54(10):961-964

Evaluation of alternative calculation methods for determining LDL cholesterol

B. Vohnout^1,2,*, A. Vachulová¹, P. Blažíček³, A. Dukát¹, G. Fodor⁴, J. Lietava¹

¹ 2nd Dept. of Internal Medicine, School of Medicine, Comenius University, Bratislava, Slovakia, head prof. Andrej Dukát, M.D., Ph.D.

² Research Laboratories, "John Paul II" Center for High Technology Research and Education in Biomedical Sciences, Catholic University of the Sacred Heart, Campobasso, Italy, head prof. Giovanni de Gaetano, M.D., Ph.D.

³ Dept. of Clinical Biochemistry, Military Hospital, Bratislava, Slovakia, head Pavol Blažíček, M.Sc.

⁴ Prevention and Rehabilitation Centre, University of Ottawa Heart Institute, Ottawa, Canada, head prof. George Fodor, M.D., Ph.D.

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 ≤ 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 ≤ 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.

Keywords: LDL-C; alternative calculation formula; Friedewald formula

Received: May 15, 2008; Accepted: June 19, 2008; Published: October 1, 2008  Show citation