Validation of the Friedewald formula for the estimation of low density lipoprotein cholesterol in a sub-Saharan African population.

Simeon-Pierre Choukem, Tasha Manases, Jean-Pierre Nda-Mefoo, Christian Akem Dimala, Yannick Mboue-Djieka, Eugene Sobngwi, Andre-Pascal Kengne

Journal: Clinical biochemistry 2018;53():25-30

PMID: 29273329

Full Text on Elsevier Science View on PubMed

Abstract

BACKGROUND

Low density lipoprotein cholesterol (LDL-C) levels are used to estimate cardiovascular disease (CVD) risk and to guide prescriptions. To circumvent the challenges of direct LDL-C measurement, guidelines recommend the use of Friedewald formula derived LDL-C levels. Despite reported limitations of this formula, its validity in sub-Saharan Africans has not been adequately investigated.

OBJECTIVE

To assess the validity of the Friedewald formula derived against directly (homogeneous) measured LDL-C in adult Cameroonians.

METHODS

We reviewed the fasting lipid profiles of 2500 patients, performed between March 2012 and January 2016 using enzymatic colorimetric method (reference), at the Douala General Hospital laboratory. The Friedewald formula was used to calculate LDL-C from total cholesterol, high density lipoprotein cholesterol and triglyceride levels. Calculated LDL-C values were compared to the reference values, and clinical significance of differences between the two methods was assessed using total error allowable (TEa).

RESULTS

The difference between means of calculated and the reference LDL-C values was neither statistically nor clinically significant (3.33±1.51 vs. 3.33±1.25mmol/l; p=0.704). The calculated LDL-C correlated positively with the measured LDL-C value (r=0.749) and both methods showed a good agreement on Bland-Altman plot. Conversely, there was only moderate agreement (kappa=0.478, 95% CI: 0.455-0.502) between the two values in the stratification of cardiovascular risk according to the National Cholesterol Education Program/Adult Treatment Panel III. Consequently, 40.6% of the participants were misclassified.

CONCLUSION

Friedewald formula is technically accurate but has a modest clinical accuracy which can translate into a substantial misclassification of patients' cardiovascular risk and subsequent inappropriate therapeutic decisions.

Address: Department of Internal Medicine and Paediatrics, Faculty of Health Sciences, University of Buea, Buea, Cameroon; Health and Human Development (2HD) Research Network, Douala, Cameroon; Department of Internal Medicine, Douala General Hospital, Douala, Cameroon. Electronic address: [email protected].; Department of Internal Medicine and Paediatrics, Faculty of Health Sciences, University of Buea, Buea, Cameroon; Health and Human Development (2HD) Research Network, Douala, Cameroon.; Biochemistry Unit, Douala General Hospital Laboratory, Douala, Cameroon; Department of Biomedical Sciences, Faculty of Medicine and Pharmaceutical Sciences, University of Douala, Douala, Cameroon.; Health and Human Development (2HD) Research Network, Douala, Cameroon; Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom.; Health and Human Development (2HD) Research Network, Douala, Cameroon.; National Obesity Centre, Yaounde Central Hospital, Yaounde, Cameroon; Department of Internal Medicine and Subspecialties, Faculty of Medicine and Biomedical Sciences, University of Yaounde 1, Yaounde, Cameroon.; South African Medical Research Council, University of Cape Town, Cape Town, South Africa.

DOI: 10.1016/j.clinbiochem.2017.12.008

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MeSH Terms: Adult, Aged, Cameroon, Cardiovascular Diseases, Cholesterol, HDL, Cholesterol, LDL, Female, Humans, Male, Middle Aged, Triglycerides