Treatment target re-classification of subjects comparing estimation of low-density lipoprotein cholesterol by the Friedewald equation and direct measurement of LDL-cholesterol

  • Anders Larsson Department of Medical Sciences, Uppsala University, Uppsala, Sweden
  • Emil Hagström Department of Medical Sciences, Uppsala University, Uppsala, Sweden; Uppsala Clinical Research Centre, Uppsala, Sweden
  • Lennart Nilsson Department of Medical and Health Sciences, Linkoping University, Linkoping, Sweden
  • Maria K. Svensson Department of Medical Sciences, Uppsala University, Uppsala, Sweden
Keywords: Direct LDL-C measurement, Friedewald equation, LDL-cholesterol, primary prevention, re-classification, secondary prevention

Abstract

Aims: To compare low-density lipoprotein cholesterol (LDL-C) values calculated by the Friedewald equation with direct LDL-C in patient samples and assess the possible impact on re-classification of LDL-C target values for primary prevention or high cardiovascular disease (CVD) risk (<2.5 mmol/L) and secondary prevention or very high CVD risk (<1.8 mmol/L). LDL-C is an important CVD risk factor. Over the last decade, there has been a change in laboratory methodology from indirectly calculated LDL-C with the Friedewald equation to direct LDL-C measurements (dLDL-C).

Methods: Reported results for plasma triglycerides, total cholesterol, high-density lipoprotein-cholesterol, and dLDL-C from 34,981 samples analyzed in year 2014 were extracted from the laboratory information system, Uppsala University Hospital, Uppsala, Sweden.

Results: dLDL-C was approximately 10% lower than the corresponding LDL-C results calculated by the Friedewald equation in both men and women. In subjects with triglyceride concentrations above 4 mmol/L (n = 1250) the same discordant pattern was seen as for the entire study population. Altogether 5469 out of 18,051 men (30.3%) and 4604 out of 16,928 women (27.2%) were down-classified at least one CVD risk category. A very small number of subject was up-classified, in total 37 out of 18,051 men (0.2%) and 28 out of 16,928 women (0.2%).

Conclusions: The two LDL-C methods had a high concordance, but the direct LDL-C measurement consistently gave approx. 10% lower values, and this caused one-third of subjects to be re-classified as having a lower cardiovascular disease risk in relation to recommended LDL-C target values and decision limits.

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Published
2018-05-10
How to Cite
Larsson, A., Hagström, E., Nilsson, L., & Svensson, M. K. (2018). Treatment target re-classification of subjects comparing estimation of low-density lipoprotein cholesterol by the Friedewald equation and direct measurement of LDL-cholesterol. Upsala Journal of Medical Sciences, 123(2), 94–99. https://doi.org/10.1080/03009734.2018.1465496
Section
Original Articles

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