Validation of the friedewald formula for low density lipoprotein cholesterol estimation in adult cameroonians

CaHReF 20116, Yaoundé Conges hall, 23 – 26 August 2016 , PL106

Faculty of Health Sciences, University of Buea, Cameroon

Low density lipoprotein cholesterol (LDLc) is a major cardiovascular risk factor. World-wide guidelines recommend Friedewald estimated LDLc for cardiovascular risk assessment and therapeutic target; because the reference method is often not available or too expensive. Various limitations of Friedewald estimated LDLc have been reported. Also, to the best of our knowledge, this formula has not been validated in the sub-Sahara Africans.
We sought to validate the Friedewald formula derived LDLc against directly measured (reference) LDLc in adult Cameroonians.

We retrospectively studied 2500 fasting lipid profiles of participants of age ≥18 years which were analysed following standard procedures with enzymatic colorimetric kit (reference), from March 2012 to January 2016 at Douala General Hospital laboratory, Cameroon. Friedewald formula was used to calculate LDLc from total cholesterol, high density lipoprotein cholesterol and triglycerides. Calculated LDLc values were compared parametrically to the reference values. Kappa statistics and Bland-Altman plot were used to determine the level of agreement between the two methods. The clinical importance of significant differences was assessed using total allowable error.

Though we found strong positive correlation between estimated and measured LDLc values, the Friedewald formula, underestimated LDLc level by 0.26 (95% CI: 0.26-0.30) mmol/l compared to the reference method. This level of underestimation was significant (p<0.001). As a consequent, the agreement between the two methods in participants’ cardiovascular risk stratification according to the National Cholesterol Education Programme/Adult Treatment Panel III was small (51.2%). All the differences were clinically significant.

The agreement between the Friedewald estimated and directly measured LDLc is poor. Friedewald-calculated LDLc may lead to wrong clinical decisions regarding cardiovascular risk stratification and lipids lowering therapeutic decision in up to half of patients. 

Friedewald formula, low density lipoprotein cholesterol, cardiovascular risk, direct homogenous assay, Cameroon.