Factors Causing Disagreement between Measured and Calculated Low Density Lipoprotein-Cholesterol (LDL-C) in Clinical Laboratory Services

BACKGROUND Since measured low density lipoprotein-cholesterol (LDL-C) has been available in clinical laboratories, there have been concern about the disagreement between measured and calculated LDL-C and the factors causing their disagreement. MATERIAL AND METHODS Serum lipid concentrations were collected from 1,339 medical records of patients admitted to hospital between 2013 and 2015. They were grouped by their total cholesterol (TC), triglycerides (TG), and high-density lipoprotein-cholesterol (HDL-C) concentrations and the agreement between measured and calculated LDL-C was statistically analyzed. RESULTS A strong relationship was found between measured and calculated LDL-C. Significantly disagreements between measured and calculated LDL-C were found in all groups in 2013 and 2014 when lipids were analyzed by Cobas C501. Disagreements found in groups of low TG and low HDL-C concentrations in 2015 were when lipids were analyzed by Abbott Architect ci8200. In groups of calculated LDL-C <1.81 mmol/L, around 80% had the measured LDL-C >1.81 mmol/L. Among various atherogenic indices, non-HDL-C showed the strongest relationship with LDL-C, while TC to HDL-C ratio showed the strongest agreement with the LDL-C. CONCLUSIONS The disagreement between measured and calculated LDL-C in a clinical laboratory seemed to depend on the analytical system used, and was probably associated with individual laboratory variations.