Validation of the friedewald formula in pre and postmenopausal women: An Indian perspective study

Introduction and Aim: The incidence of cardiovascular disease (CVD) is higher in postmenopausal women due to loss of cardioprotective effect of estrogen. Estimation of serum LDL becomes crucial in the management of CVD specially in postmenopausal women with hyperglycemia. To make lipid profile cost effective, in most of the clinical labs, estimation of LDL is done using Friedewald formula. The aim of the study is to validate serum LDL concentration estimation by Friedewald formula and compare it with a direct enzymatic method in pre and postmenopausal women. Further, examine the effect of blood glucose on LDL values in these women. Materials and Methods: The study population included 88 premenopausal and 96 post menopausal women with the median age being 32 and 48 respectively. Lipid profile and fasting blood glucose was estimated by routine spectrophotometric methods. LDL was determined by both enzymatic method and by calculation. Both pre and postmenopausal women were further subdivided into normal, prediabetic and diabetic groups. Results: LDL determined by direct assay correlated highly with calculated LDL in both premenopausal and postmenopausal women irrespective of fasting glucose level. However, the percentage error between calculated and direct LDL increased markedly with increase in glycemic status. In premenopausal women with normal blood glucose, there was no difference between calculated and direct LDL. However, as the blood glucose increased, the difference between the calculated and direct LDL was statistically significant. Calculated LDL underestimated the true serum LDL values. Further, in postmenopausal women, this difference was statistically significant in all the subgroups. Conclusion: Serum LDL concentration calculated using Friedewalds formula may not only be altered by variables like HDL and triglyceride but endogenous risk factors of CVD like the hormonal and glycemic status of the individual, add to the error of calculation.