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Calculated LDL-cholesterol: comparability of the extended Martin/Hopkins, Sampson/NIH, Friedewald and four other equations in South African patients
  1. Amber Carelse1,
  2. Helgard M Rossouw1,
  3. Nicolene Steyn1,
  4. Janine Martins2,
  5. Tahir S Pillay1
  1. 1Chemical Pathology, University of Pretoria & National Health Laboratory Service, Pretoria, Gauteng, South Africa
  2. 2Chemical Pathology, University of Pretoria, Pretoria, Gauteng, South Africa
  1. Correspondence to Professor Tahir S Pillay, Chemical Pathology, University of Pretoria, Pretoria, South Africa; tspillay{at}


Aims The reference method for low-density lipoprotein-cholesterol (LDL-C) is ultracentrifugation. However, this is unsuitable for routine use and therefore direct LDL-C assays and predictive equations are used. In this study, we compared the Friedewald, extended Martin/Hopkins, Sampson/NIH and four other equations to a direct assay.

Methods We analysed 44 194 lipid profiles from a mixed South African population. The LDL-C predictive equations were compared with direct LDL-C assay and analysed using non-parametric statistics and error grid analysis.

Results Both the extended Martin/Hopkins and Sampson/NIH equations displayed the best correlation with direct LDL-C in terms of desirable bias and total allowable error. The direct LDL-C assay classified 13.9% of patients in the low LDL-C (1.0–1.8 mmol/L) category, in comparison to the extended Martin/Hopkins equation (13.4%), the Sampson equation (14.6%) and the Friedewald equation (16.0%). The Sampson/NIH was least biased in the low LDL-C category (<1.8 mmol/L) and produced the least overall clinically relevant errors compared with the extended Martin/Hopkins and Friedewald equations in the low-LDL-C category.

Conclusions Our findings suggest only a marginal difference between the extended Martin/Hopkins equation and the Sampson/NIH equation with the use of the Beckman Coulter DxC800 analyser in this population. The results favour the implementation of the Sampson/NIH equation when the Beckman Coulter DxC analyser is used, but the extended Martin/Hopkins may also be safely implemented. Both of these equations performed significantly better than the Friedewald equation. We recommend that patients be monitored using one of these methods and that each laboratory perform its own validation of either equation to ensure continuation and accuracy, and to prevent between-method variation.

  • Medical Laboratory Science
  • Hyperlipidemias

Data availability statement

Data are available on reasonable request.

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Data availability statement

Data are available on reasonable request.

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  • Handling editor Patrick J Twomey.

  • Contributors AC: conceptualisation, analysis interpretation, resources, writing (initial manuscript, review and editing). MR: resources, writing (review and editing). NS: resources, writing (review and editing). JM: conceptualisation, writing (review and editing). TSP: conceptualisation, visualisation, project administration, supervision, writing (review and editing), guarantor.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.