Validation of multiple equations for estimating low-density lipoprotein cholesterol levels in Korean adults

Background Limited data are available for validation of low-density lipoprotein cholesterol (LDL) calculation (LDLcal) in the adult Korean population. The aim of this study was to develop and validate a new equation for LDLcal and to compare it with previous such equations in a Korean population. Methods A new equation for LDLcal was developed (LDLChoi). LDLChoi and 11 other previously published equations were applied and compared with directly measured LDL concentration (LDLdirect) in a development cohort (population 1), an independent validation cohort in the same laboratory (population 2), and the Korea National Health and Nutrition Examination Survey 2017 cohort (population 3). Results Among the 12 equations, the newly-developed equation (LDLChoi = total cholesterol – 0.87 x high-density lipoprotein cholesterol – 0.13 x triglycerides) had the highest intraclass correlation coefficient (ICC) and the lowest mean systemic difference and median absolute percentage error in populations 1 and 2 but not in population 3. Subgroup analysis showed good agreement between LDLChoi and LDLdirect (ICC > 0.75) in population 2, whose LDLdirect < 70 mg/dL. For samples with high triglycerides (> 400 mg/dL), equation accuracy varied. Categorization concordance according to the National Cholesterol Education Program Adult Treatment Panel III criteria with the other 11 equations were less than 80%; that of LDLChoi was 87.6 and 87.4% in populations 1 and 2, respectively. Conclusions Accuracy of 12 equations for LDLcal varied by cohort and subgroup based on LDLdirect and triglycerides. A laboratory-specific equation for LDLcal and/or LDLdirect may be needed for accurate evaluation of LDL status.