Best practice for LDL-cholesterol: when and how to calculate.
Level 5 - mechanism / opinion, no new human data
Narrative review of diagnostic calculation methods without systematic review methodology
PubMed 36650044 · doi:10.1136/jcp-2022-208480
What was done
This narrative review examined clinical laboratory approaches for determining low-density lipoprotein cholesterol (LDL-C). It evaluated the standard Friedewald equation, direct measurement methods, and newer calculation equations, specifically the Sampson-National Institutes of Health (NIH) equation 2 and the Martin-Hopkins equations (standard and extended).
What was found
The abstract reports calculation parameters and validity thresholds rather than comparative test performance metrics: - The Friedewald equation assumes a fixed TG:VLDL-C ratio of 5 (in mg/dL) and becomes invalid at triglyceride levels greater than 4.5 mmol/L. - Direct LDL-C measurement faces challenges including inter-assay lack of standardisation, higher cost, and distortion from mild hypertriglyceridaemia. - The Sampson-NIH2 equation, derived via beta-quantification and multiple least squares regression of TG and non-HDL-C, is applicable for triglyceride levels up to 9 mmol/L. - The standard Martin-Hopkins equation uses a 180-cell stratification matrix valid up to 4.5 mmol/L, whereas an extended version can be used up to 9.04 mmol/L. - No quantitative accuracy statistics (such as concordance rates or bias estimates) were reported in the abstract.
Why it matters
Provides clinical guidance on using updated calculation models (Sampson-NIH2 and Martin-Hopkins) to estimate LDL-C in patients with elevated triglycerides up to ~9 mmol/L, avoiding the inaccuracies of the Friedewald formula and the assay variability of direct measurements.
Limits
As a narrative review, it lacks systematic search criteria, quality appraisal, and meta-analytic pooling. The abstract provides no quantitative comparison of diagnostic accuracy between the discussed equations.
Cited by
- supports Standard clinical lipid panels calculate LDL cholesterol via a mathematical formula rather than directly measuring it.