comparison of ldl- cholesterol enzymatic method with friedewald’s formula

abstract          background and objectives: concentration low-density lipoprotein (ldl) is one of the strongest indicators of atherosclerosis and predicts the diagnosis of cardiovascular diseases. ldl measurement accuracy is very important. ldl can be measured directly, such as enzymatic and nephelometry methods or can be calculated using friedewald&apos;s formula. despite the development of enzymatic methods and ldl nephelometry still in most laboratories is calculated using friedewald&apos;s formula. the aim of this study was an investigation of correlation coefficient between two methods of measuring ldl- cholesterol levels.          methods: this descriptive cross-sectional study, performed on the 1141 patients. cholesterol, triglycerides, hdl, ldl all patients assayed by enzymatic method. for patients with triglyceride levels of less than 400 mg/dl had ldl levels were calculated by friedewald&apos;s formula. normal levels of ldl/hdl ratio of less than 3.5 were considered.           results: of the 1141 patients participating in this study, 38.3 % men and 61.7 % women. the mean patient age was 46.3 ± 16.1 years. mean serum cholesterol, triglycerides and hdl were 177.9 ± 41.1, 132.9 ± 73.2 and 45.8 ± 13.2 mg/dl, respectively. average direct and calculated ldl concentration was 82.1 ± 23.1 and 105.5 ± 35.8, respectively. the direct measurement of ldl, ldl/hdl levels in 97.1% of cases was normal, while 85.1 % of the calculation of ldl were normal. pearson correlation coefficients were obtained by two methods: 0.869 (p <0.001).          conclusion: despite the favorable correlation between two methods of measurements of ldl, the results of a calculation method is more than direct method. this can have a negative impact on the judgment of the treating physician.            key words: ldl, enzymatic method, friedewald&apos;s formula.