Performance of Four Homogeneous Direct Methods for LDL-Cholesterol

Miller, W. Greg; Waymack, Parvin P.; Anderson, F. Philip; Ethridge, Steven F.; Jayne, Eduviges C.

doi:10.1093/clinchem/48.3.489

Cited by 86 publications

(35 citation statements)

References 15 publications

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“…2,57 ± 0,55 2,75 ± 0,60 2,67 ± 0,58 TG en mmol/l (Moyenne ± écart-type) 0,97 ± 0,33 0,92 ± 0,32 0,93 ± 0,32 ± écart-type) 4,44 ± 0,62 4,65 ± 0,62 4,52 ± 0,62 C-HDL en mmol/l (Moyenne ± écart-type) 1,51 ± 0,08 1,48 ± 0,10 1,49 ± 0,08 C-LDL en mmol/l (Moyenne ± écart-type) 2,91 ± 0,65 2,99 ± 0,70 2,93 ± 0,68 TG en mmol/L (Moyenne ± écart-type) 0,98 ± 0,41 0,90 ± 0,35 0,95 ± 0,37 De nombreuses techniques de dosage du C-LDL ont été décrites (Rifai et al, 1992) et sont utilisées aussi bien dans les laboratoires de diagnostic que pour la recherche. Mais les méthodes directes de dosage du C-LDL sont les plus couramment utilisées dans les laboratoires des pays développés (Smets et al, 2001 ;Miller et al, 2002 ;McNamara et al, 2006) ; ce qui n'est pas encore le cas dans les pays du tiers monde.…”

Section: Resultatsunclassified

Intérêt de la technique de précipitation au sulfate de dextrane dans la détermination du cholestérol-LDL

Assoumanou¹,

Agniwo²,

Soumanou³

et al. 2011

International Journal of Biological and Chemical Sciences

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Le but de ce travail était de déterminer les valeurs du cholestérol-LDL (C-LDL) dans le sérum par la technique de précipitation au sulfate de dextrane et de les corréler avec celles obtenues par la formule de Friedewald. Les sera de 207 sujets (113 hommes, 94 femmes) volontaires d'âge moyen 41,49 ± 3,08 ans ont été analysés en double aveugle par les deux méthodes. Le cholestérol total (CT), le cholestérol-HDL (C-HDL) et les triglycérides (TG) ont été dosés par la méthode enzymatique en point final suivi du calcul du C-LDL par la formule de Friedewald. La précipitation du C-LDL a été réalisée au sulfate de dextrane et son dosage effectué directement sur la fraction précipitée par la méthode enzymatique. Les valeurs moyennes du C-LDL obtenues étaient de 2,67 ± 0,58 mmol/l par la formule de Friedewald et de 2,93 ± 0,68 mmol/l par la technique de précipitation au sulfate de dextrane. Les deux techniques avaient une corrélation positive avec un coefficient de corrélation r = +0,905. La technique de précipitation au sulfate de dextrane peut donc être utilisée pour le dosage du C-LDL.

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Section: Resultatsunclassified

Intérêt de la technique de précipitation au sulfate de dextrane dans la détermination du cholestérol-LDL

Assoumanou¹,

Agniwo²,

Soumanou³

et al. 2011

International Journal of Biological and Chemical Sciences

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“…This equation is found to be valid when the triacylglycerol level is less than 400 mg/dl [9]. The potential advantages of directly measuring LDL-C include the ability to measure LDL-C even when the triacylglycerol are >400 mg/dl, the ability to measure LDL-C without the need to make the three measurements needed for the calculated result, and the potential reduction of imprecision by a single measurement instead calculating the value from three measured results [10]. Moreover Friedewald equation is invalid when samples are collected in the non-fasting state or in the presence of increased triacylglycerol levels [9,11].…”

Section: [Ldl-c] = [Total Cholesterol] [Hdl-c] [Triacylglycerol]/5mentioning

confidence: 96%

Significant Differences Between LDL-cholesterol Levels Obtained by Friedewald Formula and a Direct Method

Eljamil¹,

Elhenshiri²,

Etekbali

et al. 2012

TOPROCJ

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Estimation of low density lipoprotein cholesterol (LDL-C) level in serum is considered to be the basis of classification and management of hypercholesterolemia. In most clinical laboratories, LDL-C is usually estimated indirectly with the Friedewald's equation or more accurately with direct methods. The lack of agreement between the two methods has been reported in several clinical laboratories using different methods. The present study is designed to compare LDL-cholesterol values obtained by Friedewald's formula and a direct method available in our laboratory (Dimension, RxL, SIEMENS). In the present study, we have found no significant differences between LDL-C obtained by Friedewald's formula (94.49 mg/dl ±28.81) and those determined by the direct method (93.98 mg/dl ±27.77) from samples with TG levels at <100 mg/dl (p>0.4) with correlation coefficient of 0.86. The LDL-C levels produced by Friedewald's formula were significantly lower than those obtained by the direct method when serum TG levels at 101-200 mg/dl (p <0.001) and 201-300 mg/dl (p <0.01) with correlation coefficient of 0.96 and 0.97 respectively. These differences are in agreement with those previously reported results in other laboratories. Therefore Friedewald's formula must be replaced by the direct method for better classification and management of hypercholesterolemia.

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“…In an example (16 ), based on data from Miller et al (17 ), 100 randomly collected patient samples were assayed by a commercially available LDL-cholesterol assay and by a reference assay. A nonparametric 95% confidence interval containing at least 95% of the LDL-cholesterol differences between the commercial and reference assays ranged from Ϫ0.47 to 5.66 mmol/L (Ϫ18 to 219 mg/dL).…”

Section: Treatment Of Outliersmentioning

confidence: 99%

Critique of the Guide to the Expression of Uncertainty in Measurement Method of Estimating and Reporting Uncertainty in Diagnostic Assays

Krouwer¹

2003

Clinical Chemistry

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Background:The Guide to the Expression of Uncertainty in Measurement (GUM) provides instructions for constructing uncertainty intervals for a measurement. This method is usually reserved for reference materials, but GUM has been recently proposed as a way to express uncertainty for commercial diagnostic assays. Methods: Using the official GUM standard and published applications of GUM to commercial diagnostic assays, I undertook an analysis to evaluate whether applying GUM to commercial diagnostic assays is warranted. Results: Certain important assays, such as troponin I, would not be candidates for GUM because troponin I is not a well-defined physical quantity. Unlike definitive methods, in which efforts are taken to detect and eliminate all systematic error sources, commercial assays often trade off features such as ease of use and cost with accuracy and allow systematic errors to be present as long as the overall accuracy meets the medical need goal. Laboratories are hindered in preparing GUM models because the knowledge required to specify some systematic errors is often available only to manufacturers. Some non-GUM methods to estimate uncertainty rely on observed data, which include both known and unknown sources of error. The occurrence of large, unknown errors for assays in routine use (e.g., outliers) is not unusual because diagnostic assays must be chemically specific in the presence of thousands of potentially interfering substances. There is no provision in GUM to deal with unexplained outliers, which may lead to uncertainty intervals that are not wide enough. Some clinicians assume that diagnostic assay results have little uncertainty. This situation may be made worse by including an uncertainty interval, which implies certification. Conclusions: Evaluations for accuracy (total analytical error) based on describing the distribution of result differences between commercial assays and reference methods indicate that some assays have a few results with large differences (e.g., outliers). This leads to a wide accuracy interval (total analytical error limits). It is unlikely that GUM would be able to predict these wide intervals, especially because there is little or no provision for outlier treatment in GUM. Presenting too narrow GUM uncertainty intervals to clinicians would be misleading. The modeling used by practitioners of the GUM method is potentially useful in improving quality, but commercial diagnostic assays are not ready for GUM uncertainty statements. © 2003 American Association for Clinical ChemistryAccuracy, the closeness in agreement between a test result and an accepted reference method, is a concept well known to clinical chemists. Inaccuracy, the lack of closeness in agreement (also called total analytical error), is caused by random and systematic errors. (3, 4 ). Kristiansen (5 ) described how GUM applies to diagnostic assays. Here I will describe problems with the GUM method with respect to its use for routine diagnostic assays. Kallner (6 ) and the NIST web site (7 ) provide excelle...

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Performance of Four Homogeneous Direct Methods for LDL-Cholesterol

Cited by 86 publications

References 15 publications

Intérêt de la technique de précipitation au sulfate de dextrane dans la détermination du cholestérol-LDL

Intérêt de la technique de précipitation au sulfate de dextrane dans la détermination du cholestérol-LDL

Significant Differences Between LDL-cholesterol Levels Obtained by Friedewald Formula and a Direct Method

Critique of the Guide to the Expression of Uncertainty in Measurement Method of Estimating and Reporting Uncertainty in Diagnostic Assays

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