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Published on: October 12, 2017
Comparison of calculated and direct low density lipoprotein cholesterol determinations in a routine laboratory
1Departmnent of Clinical Chemistry, College of Health Sciences, University of Nairobi, P.O Box 19676, Nairobi, Kenya.
Background:
Low density lipoprotein cholesterol (LDL-C) concentrations form the basis for treatment guidelines established for hyperlipidaemic patients. LDL-C concentrations are commonly calculated using the Friedwald formula (FF) which has several limitations. Recently, direct methods for LDL-C estimation have been developed which are suitable for routine laboratories.
Objective:
To compare serum LDL-C concentrations determined by a direct assay and the Friedwald formula.
Design:
Cross-sectional study.
Setting:
Mater Hospital Laboratory, Nairobi, Kenya.
Methods:
The clinical performance of the two methods was evaluated by analysing 211 fresh plasma samples from fasting adult patients. The samples were divided into four groups-normolipidaemic; and Types IIa, IIb and IV hyperlipidaemias.
Results:
The Friedwald formula (FF) correlated best with the direct assay in the normolipidaemic samples (r = 0.879; y= 0.468 + 0.852x). Direct LDL-C values were significantly lower than the FF in the Type IIa hyperlipidaemia samples (paired differences 0.38 +/- 0.62). There was only 65% agreement between the two methods in the borderline high LDL-C group of the National Cholesterol Education Program (NCEP) classification (LDL-C 3.36-4.14 mmol/L).
Conclusion:
There is lack of agreement between the FF and the Abbott direct LDL-C assay. If the two methods are used interchangeably, there may be confusion in the classification and control of lipid lowering medication for patients with hyperlipidaemia.
