Plasma Low-Density Lipoprotein Cholesterol Estimated by Friedewald Compared to Martin-Hopkins Equation in Nigerian...

Friedewald equation for estimation of plasma low-density lipoprotein cholesterol (LDL-C) has recently been the subject of controversies. We investigated the agreement between LDL-C calculated with the Friedewald equation (LDLC F) and novel Martin-Hopkins formula (LDL-CMH), and the influence of sex, age, and triglyceride stratification on the level of biases.

We used convenience sample of data from records of 7151 adults who underwent test for plasma lipid profile from 2014 to 2017 at a tertiary Hospital in Nigeria. During the period automated standard enzymatic methods were used for determination of plasma lipids. The Bland-Altman plot was used to evaluate the agreement between the two equations.

Participants were 2953 males and 4198 females. The age of the subjects ranged from 21 to 91 years with overall mean age of 54.2±12.1 years. The discrepancy between LDLC MH and LDL-CF ranged from -0.05 to 0.93 mmol/L (median = 0.16) with a mean value of 0.172 ±0.094 mmol/L. The BlandAltman analysis showed an estimated bias of 6.38% (95% CI = -5.02, 20.0). The bias in males and females was 8.3% (95% CI = -5.6, 22.2) and 6.9% (95% CI = -4.4, 18.3), respectively. At an average LDL-C less than 1.81 mmol/L, estimated bias became increased to 16.6% (95% CI = -6.1, 39.2). The calculated LDL-C MH were significantly higher than LDL-CF irrespective of the level of triglyceride.

Although both showed excellent reliability, the Friedewald equation resulted in a clinically lower LDL-C than the Martin-Hopkins formula. It may be necessary to pay attention to biological sex differences.