Comparison of LDL-cholesterol estimate using the Friedewald formula and the newly proposed de Cordova formula with a directly measured LDL-cholesterol in a healthy South African population.
BACKGROUND
The accurate determination of low density lipoprotein cholesterol (LDL-c) is pertinent in clinical practice. Most laboratories employ the Friedewald formula, for convenient estimation of LDL-c, despite its shortfalls. Different formulae have been proposed for use, for more accurate but convenient estimation of LDL-c. Here, we compare a new formula recently proposed by de Cordova et al., with that of Friedewald and LDL-c determined by a homogeneous assay. We also assess its performance at very low TG levels against the modified Friedewald formula recommended by Ahmadi et al.


METHODS
A database of 587 adults from the 'Establishing Reference Intervals for Selected Analytes in South Africa' study was utilized. Fasting samples were assayed for lipids. LDL-c was determined by the Daiichi method. Performance of the Friedewald and the de Cordova formulae was compared. This was exclusively repeated at very low TG levels (<1.13 mmol/L), this time, including the Ahmadi formula.


RESULTS
The Friedewald formula and the de Cordova formula both had high correlations with the direct LDL-c (r = 0.98 and r = 0.97, respectively), although the latter showed an inconsistent bias at different LDL-c levels. The two formulae had a higher correlation (r = 0.98) than the Ahmadi formula (r = 0.92) at very low TG levels.


CONCLUSIONS
The Friedewald formula showed better agreement with the direct LDL-c than the de Cordova formula, at various LDL-c levels, in our population. It also performed better than the Ahmadi formula at very low TG levels. We therefore advise that it remains the formula of choice for LDL-c estimation in South Africa.
Department of Chemical Pathology, Tygerberg Hospital and the National Health Laboratory Services, Stellenbosch University, Parow, South Africa Department of Clinical Pathology, Lagos University Teaching Hospital, Idi-Araba, Nigeri.
Chinelo P
CP
Onyenekwu
Department of Chemical Pathology, Tygerberg Hospital and the National Health Laboratory Services, Stellenbosch University, Parow, South Africa mariza@sun.ac.za.
Mariza
M
Hoffmann
Department of Biomedical Sciences, Cape Peninsula University of Technology, Bellville, South Africa PathCare Laboratories, Mediclinic Vergelegen, Somerset West, South Africa.
Francois
F
Smit
Department of Biomedical Sciences, Cape Peninsula University of Technology, Bellville, South Africa.
Tandi E
TE
Matsha
Department of Chemical Pathology, Tygerberg Hospital and the National Health Laboratory Services, Stellenbosch University, Parow, South Africa.
Rajiv T
RT
Erasmus
D000293:Adolescent; D000328:Adult; D000368:Aged; D044383:Black People; D002784:Cholesterol / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D013019:South Africa; D014280:Triglycerides / Q000097:blood; D044465:White People; D055815:Young Adult
D008078:Cholesterol, LDL; D014280:Triglycerides; D002784:Cholesterol
Lipids; analytes; evaluation of new methods; laboratory methods; statistics