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A new equation that leverages β-quantification to assess low-density lipoprotein cholesterol (LDL-C) concentration outperformed two other LDL-C formulas in recent studies, showing promise as a more accurate tool in predicting cardiovascular risk. The Sampson LDL-C equation also has no intellectual property restrictions, making it easily accessible to laboratorians, wrote Christopher Koch, PhD, and Joe M. El-Khoury, PhD, DABCC, FACB, of Yale University in Clinical Chemistry.
Although β-quantification is the gold standard for determining LDL-C concentration, this method isn’t widely used in clinical labs because of the labor, skills, and equipment required. Labs commonly use the long-standing Friedewald equation, which estimates LDL-C by subtracting high-density lipoprotein cholesterol (HDL-C) and very low-density lipoprotein cholesterol (VLDL-C) from total cholesterol.
The Friedewald equation estimates VLDL-C by dividing triglyceride concentration (mg/dL) by 5, which has led to errors. More recently, the Martin-Hopkins equation sought to address the weaknesses in the Friedewald equation by using a unique factor based on triglyceride and non-HDL-C values. However, this equation has its own limitations, with a tendency to underestimate VLDL-C in hypertriglyceridemic samples. In addition, labs might need licensing agreements to use a patented 180-factor table.
A recent article in JAMA Cardiology introduced a bivariate quadratic equation to estimate LDL-C based on the β-quantification method. Tested on 8,656 patients, the new formula from Maureen Sampson and her co-authors bested the two older equations in correlating with β-quantification LDL-C results in hypertriglyceridemic patients (triglycerides up to 800 mg/dL). Investigators also validated the new equation in an external dataset of 27,646 subjects, in which it outperformed Friedewald and Martin-Hopkins equations in correctly classifying cardiovascular risk (reducing misclassification by 35% and 30%, respectively).
“We hope that clinical laboratories would evaluate the implementation of the Sampson LDL equation in their laboratories to replace the outdated Friedewald equation or the newer but less accurate Martin-Hopkins equation,” El-Khoury said. One potential barrier to implementation: The Sampson equation uses a bivariate quadratic equation to estimate VLDL-C, “which may not be easily handled by all laboratory information systems,” he added.
Read more about this potentially game-changing LDL-C equation in Clinical Chemistry.