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Cell-free Biochemical Fluorometric Enzymatic Assay for High-throughput Measurement of Lipid Peroxidation in High Density Lipoprotein
Published on: October 12, 2017
[Multicenter evaluation of four homogenous LDL-cholesterol assays]
P Bayer1, F Veinberg, R Couderc
1Laboratoire de biochimie et Centre clinicobiologique des lipides (Arcol), Groupe Hospitalier L'Archet, Nice. bayer.p@chu-nice.fr
Insights
New direct LDL cholesterol (LDL-C) assays offer improved accuracy and convenience over the traditional Friedewald calculation, especially for patients with high triglycerides or abnormal lipoproteins. These methods provide a reliable alternative for cardiovascular risk assessment.
Area of Science:
- Clinical Chemistry
- Cardiovascular Diagnostics
- Lipid Metabolism
Background:
- International guidelines highlight the critical role of LDL cholesterol (LDL-C) assays in managing cardiovascular risk.
- The Friedewald formula is widely used for LDL-C calculation but has limitations, particularly with elevated triglycerides (TG > 4.5 mmol/L) or dyslipidemias.
- These limitations necessitate the development of direct LDL-C measurement methods for improved accuracy and broader applicability.
Purpose of the Study:
- To evaluate the performance of four new direct LDL-C assays (Daiichi, Denka Seiken, Kyowa, Wako) in a multicenter setting.
- To compare the accuracy and reproducibility of direct assays against the Friedewald calculation and reference methods.
- To assess the specificity and reliability of direct LDL-C assays in various dyslipidemic conditions.
Main Methods:
- A multicenter evaluation involving eight laboratories and 45 serum samples with TG < 3.1 mmol/L.
- Comparison of four direct LDL-C assays (Daiichi, Denka Seiken, Kyowa, Wako) with Friedewald calculation and beta-quantification.
- Testing of assay specificity using spiked lipoproteins and evaluation in patients with type III hyperlipoproteinemia.
Main Results:
- Three direct methods (Daiichi, Kyowa, Wako) demonstrated significantly improved interlaboratory reproducibility compared to Friedewald calculation.
- All tested direct methods showed strong correlation with beta-quantification, though bias varied among assays.
- VLDL-C/TG ratio influenced bias in Daiichi, Kyowa, and Wako assays; Denka Seiken was most reliable in type III hyperlipoproteinemia.
Conclusions:
- New direct LDL-C assays represent a significant technological advancement, offering enhanced analytical performance and convenience.
- These direct methods overcome the limitations of Friedewald calculation, providing a more reliable alternative for diagnosing and monitoring hyperlipidemic patients.
- Despite some assay-specific variability, direct LDL-C measurement is suitable for routine clinical use, particularly within specified triglyceride limits.
Abstract:
International guidelines emphasize the importance of LDL cholesterol (LDL-C) assay in the care and follow-up of patients with cardiovascular risk. Most studies and common practice use Friedewald's formula for LDL-C calculation. The accuracy of the result depends closely on the precision of the input parameters (total cholesterol, triglycerides (TG) and HDL cholesterol), and discrepancies between calculated LDL-C and measurement by reference methods appear when TG exceed 4.5 mmol/L, or in the presence of abnormal lipoproteins. These restrictions and uncertainties in calculations have prompted the recent development of direct and homogeneous methods that fit all analyzers. A multicenter evaluation of four direct assays of LDL-C (Daiichi, Denka Seiken, Kyowa, Wako) was carried out on 45 serum samples (TG below 3.1 mmol/L) in eight laboratories using different analyzers. For three methods (Daiichi, Kyowa, Wako), the interlaboratory reproducibility was markedly improved relative to that of calculation. A strong correlation was found for all new methods when compared with a beta-quantification assay. Average bias in Denka Seiken assays was greater than Kyowa's and Daiichi's (although less dispersed for the latter) and for Wako all bias were positive. The relationship between bias variations and the lipid parameters of the samples was studied. Three methods, Daiichi, Kyowa and Wako, revealed a significant positive correlation between bias and serum VLDL-C/TG ratio, clearly indicating that cholesterol enrichment of VLDL was a source of variability in these assays. Specificity of the four methods was tested in situation of dyslipidemia by spiking isolated lipoproteins (chylomicrons, VLDL and HDL). This experiment revealed differences in behavior, most evidently upon addition of VLDL. No method was truly specific, but up to 8 mmol/L of TG the variations were acceptable. In the presence of type III hyperlipoproteinemia, however, only the Denka Seiken method was reliable. Linearity up to 20 mmol/L (Daiichi, Denka Seiken) or 14 mmol/L (Kyowa, Wako) of LDL-C allows these tests to be used in main routine cases. New direct assays are an obvious technological advance in terms of analytical performance and conveniency. Their use for the diagnosis and follow-up of hyperlipidemic patients offers an alternative that overcomes the limitations of the Friedewald calculation.
