The clinical impact of estimating low-density lipoprotein cholesterol (LDL-C) using different equations in the general population.

BACKGROUND: Low-density lipoprotein cholesterol (LDL-C) is associated with atherosclerotic cardiovascular disease (ASCVD). Friedewald, Sampson, and Martin-Hopkins equations are used to calculate LDL-C. This study compares the impact of switching between these equations in a large geographically defined population. MATERIALS AND METHODS: Data for individuals who had a lipid panel ordered clinically between 2010 and 2019 were included. Comparisons were made across groups using the two-sample t-test or chi-square test as appropriate. Discordances between LDL measures based on clinically actionable thresholds were summarized using contingency tables. RESULTS: The cohort included 198,166 patients (mean age 54 years, 54% female). The equations perform similarly at the lower range of triglycerides but began to diverge at a triglyceride level of 125 mg/dL. However, at triglycerides of 175 mg/dL and higher, the Martin-Hopkins equation estimated higher LDL-C values than the Samson equation. This discordance was further exasperated at triglyceride values of 400 to 800 mg/dL. When comparing the Sampson and Friedewald equations, at triglycerides are below 175 mg/dL, 9% of patients were discordant at the 70 mg/dL cutpoint, whereas 42.4% were discordant when triglycerides are between 175 and 400 mg/dL. Discordance was observed at the clinically actionable LDL-C cutpoint of 190 mg/dL with the Friedewald equation estimating lower LDL-C than the other equations. In a high-risk subgroup (ASCVD risk score > 20%), 16.3% of patients were discordant at the clinical cutpoint of LDL-C < 70 mg/dL between the Sampson and Friedewald equations. CONCLUSIONS: Discordance at clinically significant LDL-C cutpoints in both the general population and high-risk subgroups were observed across the three equations. These results show that using different methods of LDL-C calculation or switching between different methods could have clinical implications for many patients.

Choosing the right equation for calculating indirect LDL-Cholesterol (LDL-C) in adult Pakistani population: Evaluation of seven equations using big data analytics.

Objective: Cardiovascular diseases (CVDs) are a leading cause of mortality worldwide. Low density lipoprotein cholesterol (LDL-C) contributes to the atherogenic process. However, direct LDL-C (d-LDL) has rarely been estimated by the gold standard method because it is cumbersome and expensive. We aim to evaluate calculated low density lipoprotein (LDL-c) by various equations with reference to directly measured LDL-C in the Pakistani adult population as a cost-effective alternative. Methods: We retrospectively evaluated the validity of seven equations for estimating calculated LDL-C by computing correlation coefficients (r) and Bland Altman plots to assess agreement (mean %) for (d-LDL) and calculated (LDL-c) on all seven equations. Statistical analysis was performed in Stata Statistical Software: Release 17, College Station, TX: StataCorp LLC. Results: We analyzed 247082 direct assays of lipid profiles of adults aged ≥18 years. The mean LDL-C levels computed on Friedewald, de Cordova, Chen, Hattori, Vujovic, Teerakanchana, Sampson equations were 106.8 ± 31.4, 103.7 ± 25.0, 108.6 ± 28.2, 100.1 ± 29.5, 115.2 ± 31.2, 113.1 ± 28.3 and 110.3 ± 30.6 respectively. Friedewald and Hattori equations correlated strongly with direct LDL-C (r = 0.937) for each followed by Sampson (r = 0.935) and Vujovic (r = 0.931). However, the median bias was least for the Friedwald equation (-1.6) compared to the other equations. Conclusion: In contrast to the global literature advocating for the use of newer equations, although the conventional and widely utilized Friedewald equation remains the best alternative for calculated LDL-C estimation in adult Pakistani population.

Comparison of the Friedewald and Vujovic methods with the calculated LDL concentration in a biochemical auto-analyzer.

Objective: To compare the concentration of Low-Density Lipoprotein (LDL-c) obtained using the Friedewald formula with those obtained directly with the RAYTO CHEMRAY 120 autoanalyzer. Methods: Cross-sectional study. We evaluated outpatients with a medical request for a lipid profile study (total cholesterol, triglycerides, LDL, and HDL). The analyses were carried out in a RAYTO CHEMRAY 120 autoanalyzer under the principle of spectrophotometry. We obtained LDL-c using the Friedewald and Vujovic formulas. Results: We evaluated 199 individuals whose direct LDL concentration averages were measured by the RAYTO CHEMRAY 120 equipment. Those calculated by the Friedewald and Vujovic formulas were 129.97 ± 32.66, 119.28 ± 30.44, and 127.01 ± 32.01, respectively, and in all cases, significant differences (P < 0.001) were observed with the RAYTO analyzer. In both cases a low positive bias was found with the RAYTO analyzer.. The Passing-Bablok and Deming's regressions showed a linear correlation between both methods (Friedewald and Vujovic) with the LDL values obtained with the Rayto autoanalyzer. Conclusions: Our study found that the Friedewald and Vujovic methods are good predictors of LDL cholesterol levels and have a low level of bias. Therefore, they could be used as potential predictors.

Objetivo: Comparar las concentraciones de Lipoproteínas de Baja Densidad (LDL-c) obtenidas mediante la fórmula de Friedewald con las obtenidas directamente con el autoanalizador RAYTO CHEMRAY 120. Métodos: Estudio transversal. Se evaluaron pacientes ambulatorios con solicitud médica de perfil lipídico (colesterol total, triglicéridos, LDL y HDL). Los análisis se realizaron con un autoanalizador RAYTO CHEMRAY 120 bajo el principio de espectrofotometría. Obtuvimos el LDL-c usando las fórmulas de Friedewald y Vujovic. Resultados: Se evaluaron 199 individuos cuyos promedios directos de concentración de LDL fueron medidos con el equipo RAYTO CHEMRAY 120. Las concentraciones calculadas por las fórmulas de Friedewald y Vujovic fueron de 129,97 ± 32,66, 119,28 ± 30,44, y de 127,01 ± 32,01, respectivamente, y en todos los casos se observaron diferencias significativas (P < 0,001) con el analizador RAYTO. En ambos casos se encontró un sesgo positivo bajo en el analizador RAYTO. Las regresiones de Passing-Bablok y Deming mostraron una correlación lineal entre ambos métodos (Friedewald y Vujovic) con los valores de LDL obtenidos con el autoanalizador Rayto. Conclusión: Nuestro estudio encontro que los métodos de Friedewald y Vujovic son buenos predictores de los niveles de colesterol LDL y presentan un nivel de sesgo bajo. Por lo que podrían usarse como potenciales predictores.

Comparison between the Friedewald, Martin and Sampson Equations and LDL-C Quantification by Ultracentrifugation in a Mexican Population.

Low-density lipoprotein cholesterol (LDL-C), which makes up about 70% of the cholesterol in the blood, is critical in the formation of arteriosclerotic plaques, increasing the risk of heart disease. LDL-C levels are estimated using Friedewald, Martin and Sampson equations, though they have limitations with high triglycerides. Our aim is to compare the effectiveness of these equations versus the ultracentrifugation technique in individuals with and without dyslipidemia and identify precision. There were 113 participants, 59 healthy controls and 54 dyslipidemic patients. Samples were collected after fasting. LDL-C was estimated using the Friedewald, Martin and Sampson equations. The purified LDL-C, ultracentrifugated and dialysized control group without dyslipidemia vs. patients with coronary artery disease (CAD) showed differences in age, HDL-C, triglycerides and glucose non-HDL-C (p = 0.001 in all). There were correlations in CGWD between ultracentrifugation and Sampson R-squared (R2) = 0.791. In the dyslipidemia control group, ultracentrifugation and Friedewald R2 = 0.911. In patients with CAD, correlation between ultracentrifugation and Sampson R2 = 0.892; Bland-Altman confirmed agreement in controls without dyslipidemia. The Martin and Sampson equations are interchangeable with ultracentrifugation. Conclusion: The role of LDL analysis using precise techniques is necessary to obtain better control of disease outcomes after the use of precise therapies and suggests verifying its importance through clinical trials.

A comparative evaluation of low-density lipoprotein cholesterol estimation: Machine learning algorithms versus various equations.

BACKGROUND: Given the critical importance of Low-density lipoprotein cholesterol (LDL-C) levels in determining cardiovascular risk, it is essential to measure LDL-C accurately. Since the Friedewald formula generates incorrect predictions in many circumstances, new equations have been developed to overcome the Friedewald equations' shortcomings. This study aimed to compare estimated LDL-C with directly measured LDL-C (dLDL-C), as well as their performance in predicting LDL-C, utilizing Friedewald, extended Martin-Hopkins, Sampson, de Cordova, and Vujovic formulas and five machine learning (ML) algorithms. METHODS: A total of 29,504 samples from the ISLAB-2 Core Laboratory were included in the study. All statistical analysis was performed using R version 4.1.2. Statistical Language. RESULTS: Bayesian-Regularized Neural Network (BRNN) (r = 0.957) and Random Forest (RF) (r = 0.957) algorithms showed a higher correlation with dLDL-C than the other equations in all-testing dataset. All ML algorithms demonstrated less bias than pre-existing LDL-C equations with dLDL-C and outperformed the LDL-C estimation equations in terms of concordance in all-testing dataset. CONCLUSIONS: The results of our research indicate that when compared to conventional equations, ML algorithms are much more effective in predicting LDL-C. ML algorithms, aided by a vast dataset, could have the capability to predict LDL-C levels even in cases where triglyceride levels are high, unlike the limited usage of Friedewald formula.

Prediction of low-density lipoprotein cholesterol levels using machine learning methods.

OBJECTIVE: Low-density lipoprotein cholesterol (LDL-C) has been commonly calculated by equations, but their performance has not been entirely satisfactory. This study aimed to develop a more accurate LDL-C prediction model using machine learning methods. METHODS: The study involved predicting directly measured LDL-C, using individual characteristics, lipid profiles, and other laboratory results as predictors. The models applied to predict LDL-C values were multiple regression, penalized regression, random forest, and XGBoost. Additionally, a novel 2-step prediction model was developed and introduced. The machine learning methods were evaluated against the Friedewald, Martin, and Sampson equations. RESULTS: The Friedewald, Martin, and Sampson equations had root mean squared error (RMSE) values of 12.112, 8.084, and 8.492, respectively, whereas the 2-step prediction model showed the highest accuracy, with an RMSE of 7.015. The LDL-C levels were also classified as a categorical variable according to the diagnostic criteria of the dyslipidemia treatment guideline, and concordance rates were calculated between the predictive values obtained from each method and the directly measured ones. The 2-step prediction model had the highest concordance rate (85.1%). CONCLUSION: The machine learning method can calculate LDL-C more accurately than existing equations. The proposed 2-step prediction model, in particular, outperformed the other machine learning methods.

The Evaluation of Lipid-Lowering Treatment in Patients with Acute Coronary Syndrome in a Hungarian Invasive Centre in 2015, 2017, and during the COVID-19 Pandemic-The Comparison of the Achieved LDL-Cholesterol Values Calculated with Friedewald and Martin-Hopkins Methods.

Background/Objectives: Patients with acute coronary syndrome (ACS) represent a vulnerable population. We aimed to investigate serum lipid levels of patients with ACS upon admission and during one year of the COVID-19 pandemic in a rural county hospital, and compared these findings with the data of patients with ACS in 2015 and 2017. The secondary aim of this paper was the comparison of the LDL-C values calculated with the Friedewald and Martin-Hopkins methods. Methods: A retrospective analysis of lipid-lowering data of patients treated with ACS in 2015, 2017 and in a COVID-19 year (1 April 2020-31 March 2021) was performed; the patient's numbers were 454, 513 and 531, respectively. Results: In the COVID-19 period one year after the index event, only 42% of the patients had lipid values available, while these ratios were 54% and 73% in 2017 and in 2015, respectively. Using the Friedewald formula, in the COVID-19 era the median of LDL cholesterol (LDL-F) was 1.64 (1.09-2.30) mmol/L at six months and 1.60 (1.19-2.27) mmol/L at one year, respectively. These values were 1.92 (1.33-2.27) mmol/L and 1.73 (1.36-2.43) mmol/L using the Martin-Hopkins method (LDL-MH). The LDL-F yielded significantly lower values (15% lower at six months, p = 0.044; and 8% lower at one year, p = 0.014). The LDL-F reached the previous target of 1.8 mmol/L during the COVID-19 pandemic 36% at one year vs. 48% in 2017, and 37% in 2015. The recent target LDL-C level of 1.4 mmol/L was achieved in 22% of cases in the COVID-19 pandemic, 16% in 2015 and 19% in 2017. Conclusions: A significantly lower proportion of patients with ACS had available lipid tests during the COVID-19 pandemic. Besides the lower number of available samples, the proportion of achieved 1.4 mmol/L LDL-C target lipids was stable. More rigorous outpatient care in the follow-up period may help to improve the quality of lipid lowering treatments and subsequent secondary cardiovascular prevention. If direct LDL-C determination is not available, we prefer the LDL calculation with the Martin-Hopkins method.

A Novel LDLC Equation is Superior to the NIH LDLC Equation and the Friedewald Equation.

Background: LDLC equations have varying levels of underestimation for the calculated LDLC. Therefore, underestimating LDLC should be avoided as much as possible. We need to establish LDLC equations that underestimate LDLC as little as possible. Methods: We established the equations with a healthy cohort from Shuyang Hospital and validated the equations with an unselected patient cohort from The Second People's Hospital of Lianyungang. We established the novel LDLC equations by using the regression equation. The relationship between two markers was analysed using Pearson's approach. The 95% limits of measuring agreement within ±2 SD for the LDLC equations was performed using Bland‒Altman analysis. ROC curve analysis was used to predict LDLC levels and the accuracy of the LDLC equation for determining the direct LDLC levels at LDLC cut-offs was assessed. Results: We obtained two novel LDLC equations (LDL_nonHDLC equation=-0.899+1.195*nonHDLC-0.00347*nonHDLC2 and LDL_TC(total cholesterol) equation=-2.775+1.29*TC -0.00990* TC 2). The correlation coefficient between the novel LDLC equation and the direct LDLC measurements is not lower than that between the LDL_NIH equation and the direct LDLC measurements. The AUCs of our novel LDLC equations were greater than those of the LDL_NIH equation and the LDL_F equation at the LDLC cut-offs for clinical decision-making. The measuring agreement in the methods of the LDL_nonHDL equation is superior to that of the LDL_NIH equation. Conclusion: LDLC calculated by the novel LDL_nonHDL equation exhibited superiority over the LDL_NIH equation. Combining the LDL_NIH equation and our novel LDLC equation may improve accuracy and avoid undertreatment of high LDLC levels.

Comparación de los métodos de Friedewald y Vujovic con la concentración de LDL calculada en un autoanalizador bioquímico / Comparison of the Friedewald and Vujovic methods with the calculated LDL concentration in a biochemical auto-analyzer

Objective To compare the concentration of Low-Density Lipoprotein (LDL-c) obtained using the Friedewald formula with those obtained directly with the RAYTO CHEMRAY 120 autoanalyzer. Methods Cross-sectional study. We evaluated outpatients with a medical request for a lipid profile study (total cholesterol, triglycerides, LDL, and HDL). The analyses were carried out in a RAYTO CHEMRAY 120 autoanalyzer under the principle of spectrophotometry. We obtained LDL-c using the Friedewald and Vujovic formulas. Results We evaluated 199 individuals whose direct LDL concentration averages were measured by the RAYTO CHEMRAY 120 equipment. Those calculated by the Friedewald and Vujovic formulas were 129.97 ± 32.66, 119.28 ± 30.44, and 127.01 ± 32.01, respectively, and in all cases, significant differences (P < 0.001) were observed with the RAYTO analyzer. In both cases a low positive bias was found with the RAYTO analyzer.. The Passing-Bablok and Deming's regressions showed a linear correlation between both methods (Friedewald and Vujovic) with the LDL values obtained with the Rayto autoanalyzer. Conclusions Our study found that the Friedewald and Vujovic methods are good predictors of LDL cholesterol levels and have a low level of bias. Therefore, they could be used as potential predictors.

Objetivo Comparar las concentraciones de Lipoproteínas de Baja Densidad (LDL-c) obtenidas mediante la fórmula de Friedewald con las obtenidas directamente con el autoanalizador RAYTO CHEMRAY 120. Métodos Estudio transversal. Se evaluaron pacientes ambulatorios con solicitud médica de perfil lipídico (colesterol total, triglicéridos, LDL y HDL). Los análisis se realizaron con un autoanalizador RAYTO CHEMRAY 120 bajo el principio de espectrofotometría. Obtuvimos el LDL-c usando las fórmulas de Friedewald y Vujovic. Resultados Se evaluaron 199 individuos cuyos promedios directos de concentración de LDL fueron medidos con el equipo RAYTO CHEMRAY 120. Las concentraciones calculadas por las fórmulas de Friedewald y Vujovic fueron de 129,97 ± 32,66, 119,28 ± 30,44, y de 127,01 ± 32,01, respectivamente, y en todos los casos se observaron diferencias significativas (P < 0,001) con el analizador RAYTO. En ambos casos se encontró un sesgo positivo bajo en el analizador RAYTO. Las regresiones de Passing-Bablok y Deming mostraron una correlación lineal entre ambos métodos (Friedewald y Vujovic) con los valores de LDL obtenidos con el autoanalizador Rayto. Conclusión Nuestro estudio encontro que los métodos de Friedewald y Vujovic son buenos predictores de los niveles de colesterol LDL y presentan un nivel de sesgo bajo. Por lo que podrían usarse como potenciales predictores.

Concordancia entre la medición directa y el valor estimado de colesterol de LDL en pacientes ambulatorios / Concordance between direct measurement and estimated LDL cholesterol in outpatients / Concordância entre medição direta e colesterol LDL estimado em pacientes ambulatoriais

Los laboratorios clínicos estiman la concentración del colesterol asociado a la lipoproteína de baja densidad (cLDL) mediante la ecuación de Friedewald; sin embargo, ésta presenta una notable desviación cuando la concentración sérica de triglicéridos se encuentra elevada. Se compararon 4.644 resultados de cLDL valorados en el laboratorio central del Hospital Edgardo Rebagliati Martins (Lima-Perú), mediante el ensayo directo homogéneo, con los valores estimados por las ecuaciones de Friedewald, Anandaraja, Chen, Vujovic, Córdova y de regresión múltiple. Además, se estratificaron los resultados en 5 grupos en función de las concentraciones de triglicéridos para determinar la influencia que ejerce el nivel de triglicéridos sobre dichas ecuaciones. En el total de las estimaciones, las ecuaciones de regresión y Vujovic mostraron los menores sesgos de -3,00 y -2,90 mg/dL, respectivamente. Asimismo, ambas ecuaciones presentaron un grado de acuerdo sustancial con la determinación directa y un menor error sistemático en los tres niveles de decisión clínica para el cLDL; sin embargo, la ecuación de regresión presentó una mejor performance para estimar el cLDL en concentraciones de triglicéridos ≥401 mg/dL. Se concluye que la ecuación de regresión presenta bajo error analítico, además de mostrar una buena concordancia con el método directo, incluso a concentraciones altas de triglicéridos.

Clinical laboratories estimate the concentration of low-density lipoprotein cholesterol (LDLc) associated with the Friedewald equation, but the latter shows a significant deviation when the serum triglyceride concentration is elevated. A total of 4644 LDLc values assessed at the central laboratory of the Edgardo Rebagliati Martins Lima-Perú Hospital were compared by means of the homogeneous direct assay with the values estimated by the Friedewald, Anandaraja, Chen, Vujovic, Córdova and multiple regression equations. Besides, the results were stratified into 5 groups based on triglyceride concentrations to determine the influence exerted by the triglyceride level on these equations. In the total of the estimates, the regression equations and Vujovic showed the lowest biases of -3.00 and -2.90 mg/dL respectively. Likewise, both equations presented a degree of substantial agreement with the direct determination and a smaller systematic error in the three levels of clinical decision for LDLc. However, the regression equation showed a better performance for estimating LDLc at triglyceride concentrations ≥401 mg/dL. It is concludeasdasdd that the regression equation presents low analytical error, besides showing a good concordance with the direct method even at high triglyceride concentrations.

Laboratórios clínicos calculam a concentração do colesterol associado à lipoproteína de baixa densidade (LDLc), utilizando a equação de Friedewald; no entanto ela apresenta um desvio significativo quando a concentração sérica de triglicerídeos está elevada. 4644 resultados de LDLc foram comparados avaliados no laboratório central do Hospital Edgardo Rebagliati Martins (Lima-Peru), por ensaio directo homogêneo, com os valores estimados pelas equações Friedewald, Anandaraja, Chen, Vujovic, Córdova e de regressão múltipla. Além disso, foram estratificados os resultados em cinco grupos com base nas concentrações de triglicerídeos para determinar a influência que exerce o nível de triglicerídeos sobre tais equações. No total das estimativas, as equações de regressão e Vujovic mostraram os menores vieses de -3,00 e -2,90 mg/DL, respectivamente. Também, ambas as equações apresentaram um grau substancial de acordo com a determinação direta e um menor erro sistemático nos três níveis de decisão clínica para o LDLc; contudo, a equação de regressão apresentou melhor desempenho para estimar o LDLc em concentrações de triglicerídeos ≥401 mg/dL. Conclui-se que a equação de regressão apresenta baixo erro analítico, além de mostrar boa concordância com o método direto, mesmo em altas concentrações de triglicerídeos.

Valores de colesterol LDL en una población adulta de referencia / LDL cholesterol values in a reference mature population

Se llevó a cabo un estudio descriptivo de 205 usuarios del Laboratorio Central del Hospital Provincial Docente Clinicoquirúrgico "Saturnino Lora Torres" de Santiago de Cuba, desde diciembre del 2013 hasta igual periodo del 2014, a fin de determinar los niveles de referencia de colesterol LDL por el método enzimático e identificar variaciones en las estimaciones del analito según 2 metodologías. Se aplicó la prueba estadística paramétrica de Anderson Darling. Predominaron el sexo masculino, el adulto joven y los pacientes normopeso. Se establecieron los valores de referencia para el colesterol LDL por método directo de 1,37 a 4,89 mmol/L para la población general. Se obtuvo un coeficiente de correlación de Pearson de 0,82 entre el método directo y la fórmula de Friedewald. Los valores obtenidos no se encontraron contenidos en el rango clínico establecido para este analito y aunque ambas metodologías se asociaron, dichos valores fueron marcadamente inferiores para el método calculado.

A descriptive study of 205 users of the Central Laboratory of "Saturnino Lora Torres" Teaching Clinical Surgical Provincial Hospital in Santiago de Cuba was carried out from December, 2013 to the same period in 2014, in order to determine the reference levels of LDL cholesterol for the enzymatic method and identify estimates variations of analito according to 2 methodologies. Anderson Darling's parametric statistical test was applied. Male sex, young adult and the patients with normal weight prevailed. The reference values were established for LDL cholesterol by direct method from 1.37 to 4.89 mmol/L for the general population. A Pearson correlation coefficient of 0.82 was obtained between the direct method and the Friedewald formula. The obtained values were not contained in the established clinical range for this analito and although both methodologies were associated, such values were markedly inferior for the calculated method.

DETERMINACIÓN DE LOS NIVELES DE COLESTEROL LDL COMPARANDO EL MÉTODO PRECIPITADO VS LA FÓRMULA DE FRIEDEWALD EN CANINOS / DETERMINATION OF LDL CHOLESTEROL LEVELS OF COMPARING THE PRECIPITATE METHOD VS THE FRIEDEWALD FORMULA CANINE

El objetivo del presente estudio fue comparar el método de precipitación con el método de fórmula de Friedewald para la determinación de colesterol LDL en caninos. Para ello, se tomaron muestras de sangre de 185 caninos adultos en estado de ayuno de diferente raza y sexo. Se determinaron los niveles de colesterol LDL mediante el método precipitado y posteriormente con el método de Friedewald. Los resultados fueron analizados estadísticamente mediante ANOVA de una vía. El método precipitado reportó valores en mg/dl de: 52,40 promedio; 2,66 mínimo; 132,67 máximo; 130,01 rango y 24,29 de desviación estándar. Por su parte, los valores del método de Friedewald en mg/dl fueron: 65,19 promedio; 4,55 mínimo; 184,20 máximo; 179,65 rango y 31,51 de desviación estándar. El valor de p en el test F fue menor a 0.05, indicando diferencia estadísticamente significativa entre los dos métodos analizados con un nivel de confianza del 95,0%. En conclusión se recomienda utilizar el método precipitado para la determinación de los niveles de colesterol LDL en caninos.

The objetive of this study was to compare the precipitation method with the method of Friedewald formula for the determination ofLDL cholesterol in dogs. For that, blood samples of 185 overnight fasted adult dogs of different breed and sex were obtained. Blood levels of LDL cholesterol were determined by the precipitation method and later by the Friedewald method. The results were analyzed using one way ANOVA. The precipitate method reported values in mg/dl of: 52.40 average, 2.66 minimum, 132.67 maximum, 130.01 range and 24.29 of standard deviation. For its part, the Friedewald equation values in mg/dl were: 65.19 average, 4.55 minimum, 184.20 maximum, 179.65 range and 31.51 of standard deviation. The p-value in the F test was less than 0.05, indicating statistically significant difference between the two methods analyzed with a confidence level of 95.0%. In conclusion it can be used the precipitated method for determining LDL cholesterol levels in dogs.

Colesterol -LDL: ¿determinación química, fórmula de Friedewald o análisis de Regresión ? / LDL cholesterol: Direct homogeneous assay, Friedewald formula, or regression analysis?

La elevación del colesterol de la lipoproteína de baja densidad (C-LDL) es una de las principales causas de riesgo cardiovascular. Pese a la existencia de métodos analíticos para medir la concentración de C-LDL, el uso de la fórmula de Friedewald permite estimar su valor a partir de los valores de colesterol, triglicéridos y colesterol de la lipoproteína de alta densidad (C-HDL). Nuestro objetivo fue el evaluar la validez de la utilización de la fórmula, comparándola con la medida directa del C-LDL y el análisis de regresión múltiple a partir de datos de muestras de pacientes pediátricos. Se realizo un análisis de regresión lineal múltiple. La ecuación de regresión obtenida fue: C-LDL= -1,5988 + (0,845168*CT)-(0,0966192*TG)-(0,80157*C-HDL)+ (1,13943*sexo). Este modelo resulta satisfactorio (p-valor < 0,00001) ya que explica el 95,43% del comportamiento de las C-LDL con un valor de R2 = 0,9543. Los valores de C-LDL predichos con la ecuación de regresión presentaron un valor 97,26 ± 35,57 mg/dl, no mostrando diferencias significativas (p-valor=0,981) con los valores hallados con el método homogéneo 97,47 ± 36,55 mg/dl lo que permitiría su aplicación en nuestro laboratorio (AU)

High low-density lipoprotein (LDL) cholesterol levels is one of the main causes of cardiovascular risk. Although different analytical methods exist, the Friedewald formula allows to estimate LDL based on total cholesterol, triglyceride, and high-density lipoprotein (HDL) cholesterol levels. Our aim was to evaluate the validity of the formula comparing it to direct LDL-cholesterol measurement using multiple linear regression analysis of the data of samples of pediatric patients. Performing multiple regression analysis, the regression equation obtained was: LDL cholesterol =-1.5988+(0.845168*CT)- (0.0966192*TG)-(0.80157*HDL cholesterol)+(1.13943*sex). The model proved to be satisfactory (p-value < 0.00001) as it confirmed 95.43% of the LDL cholesterol levels with an R2 value = 0.9543. The LDL cholesterol levels predicted by regression equation were 97.26 ± 35.57 mg/dl, not showing significant differences (p-value=0.981) compared with levels found using the homogeneous method (97.47 ± 36.55 mg/dl) allowing its use in our laboratory (AU)

Medida del colesterol de lipoproteínas de baja densidad utilizando tres metodologías / Measurement of cholesterol low-density lipoprotein using three methodologies / Medida do colesterol de lipoproteínas de baixa densidade utilizando tres metodologias

Tomando en cuenta que aún no existe una metodología estándar de rutina para la determinación del colesterol de lipoproteínas de baja densidad (LDL-c) se decidió evaluar su determinación analítica utilizando tres técnicas: determinación enzimática homogénea, precipitación con sulfato de polivinilo y fórmula de Friedewald. Fueron procesadas 98 muestras de suero a las cuales se les determinó triglicéridos (TG), colesterol total (CT), colesterol de lipoproteínas de alta densidad (HDL-c) y colesterol de lipoproteínas de baja densidad (LDL-c). Los valores promedio de CT fueron 194,46 ± 43,54 mg/dL, HDL-c 51,12 ± 12,36 mg/dL y TG 132,88 ± 76,93 mg/dL. Aun cuando el análisis de regresión mostró una buena correlación entre los valores de LDL-c, los resultados indicaron una diferencia estadísticamente significativa en los mismos cuando los niveles de TG superaron los 200 mg/dL. La misma se observó principalmente entre el método de precipitación y la fórmula de Friedewald, siendo los valores significativamente más bajos en esta última (LDL-c por precipitación: 141,3 ± 26,2 mg/dL; LDL-c por fórmula de Friedewald: 110,1 ± 35,4 mg/dL). De la misma manera se vio afectada la proporción de individuos clasificados según su riesgo coronario. Es necesario comparar las técnicas aplicadas en este estudio con la cuantificación beta para evaluar cuál tiene un mayor nivel de exactitud.

Considering that there is still no standard methodology for routine determination of low density lipoprotein (LDL-c) it was decided to evaluate their analytical determination using three techniques: homogeneous enzymatic determination, polyvinyl sulphate precipitation and Friedewald formula. Ninety-eight serum samples were processed; triglycerides (TG), total cholesterol (TC), high-density lipoprotein (HDL-c) and LDL-c were determined. Mean total cholesterol was 194.46 ± 43.54 mg/dL, HDL-C was 51.12 ± 12.36 mg/dL and TG was 132.88 ± 76.93 mg/dL. Although regression analysis showed a good correlation between LDL-c, the results showed a statistically significative difference in them when TG levels exceeded 200 mg/dL. It was mainly observed in the precipitation method and the Friedewald formula, the latter values being significantly lower (LDL-C by precipitation: 141.3 ± 26.2 mg/dL, LDL-C by the Friedewald formula: 110, 1 ± 35.4 mg/dL). Moreover, this difference affected the proportion of individuals classified according to their coronary risk. It is necessary to compare the techniques applied in this study with beta quantification to assess which has a higher level of accuracy.

Levando em consideragao que ainda nao existe uma metodologia padrao de rotina para a determinagao do colesterol de lipoproteínas de baixa densidade (LDL-c) se decidiu avaliar sua determinagao analítica utilizando tres técnicas: determinagao enzimática homogénea, precipitagao com sulfato de polivinil e fórmula de Friedewald. Foram processadas 98 amostras de soro as quais lhes foi determinado triglicerídeos (TG), colesterol total (CT), colesterol de lipoproteínas de alta densidade (HDL-c) e colesterol de lipoproteínas de baixa densidade (LDL-c). Os valores médios de CT foram 194,46 ± 43,54 mg/dL, HDL-c 51,12 ± 12,36 mg/dL e TG 132,88 ± 76,93 mg/dL. Inclusive quando a análise de regressao mostrou uma boa correlagao entre os valores de LDL-c, os resultados indicaram uma diferenga estatisticamente significativa nos mesmos quando os niveis de TG superaram os 200 mg/dL. A mesma se observou principalmente entre o método de precipitagao e a fórmula de Friedewald, sendo os valores significativamente mais baixos nesta última (LDL-c por precipitagao: 141,3 ± 26,2 mg/dL; LDL-c por fórmula de Friedewald: 110,1 ± 35,4 mg/dL). Da mesma maneira se viu afetada a proporgao de indivíduos classificados conforme seu risco coronariano. É necessário comparar as técnicas aplicadas neste estudo com a quantificagao beta para avaliar qual é que tem maior nível de exatidao.

Comparison of low-density lipoprotein obtained from the Friedewald formula and new formulae in a heterogeneous population / Comparación de lipoproteínas de baja densidad obtenidas por fórmula de Friedewald y nuevas fórmulas en una población heterogénea

Introduction: Although the levels of low-density lipoprotein (LDL-C) should ideally be determined by beta quantification or enzymatic methods, there are limitations in developing countries. The goal of this study is to compare LDL-C obtained through three formulae (LDL-Cnf) with LDL-C obtained through the Friedewald formula (LDL-Cf) using LDL-C through enzymatic methods as the most-accepted reference method in clinical practice (LDL-Cr). Methods: A concordance study was carried out in a reference laboratory in Cali, Colombia. The three formulae were (mg/dl): Men with triglycerides under 400 mg/dl: LDL-C = Total Cholesterol (TC) - triglycerides (TG) /6.5) - 45; men with triglycerides equal to or greater than 400 mg/dl: LDL-C = (TC - (TG / 7)) -50 and women: LDL-C = (TC-(TG /6.5)) - 70. Results: Three-hundred fifteen values were obtained of which 53% were for women. The mean age and LDL-Cr were 54 years (±15.8) and 112.1 mg/dl (±32.5), respectively. The median (interquartile range, mg/dl) of TC, high-density lipoprotein (HDL-C) and TG were 204 mg/dl (171-229), 51 mg/dl (41-61), and 156 mg/dl (99-237), respectively. There were no differences between mean values of LDL-Cr and LDL-Cnf (113.48 vs. 112.67 mg/dl; p=0.45). The intraclass correlation coefficient among LDL-Cr and LDL-Cf and LDL-Cnf were high (R=0.93 and 0.92, respectively). The correlation between LDL-Cf and LDL-Cnf was 0.95. There is no difference between the areas under the  receiver operating characteristic (ROC) curve with the level of LDL-Cr at 160 mg/dl for LDL-Cnf and LDL-Cf. (0.94 vs. 0.93; p=0.27). Conclusion: There is high concordance between LDL-Cf and LDL-Cnf. These formulae could be an alternative when there are limitations to determine LDL-C because of the lack of enzymatic methods or through Friedewald formula due to the absence of HDL-C.

Introducción: Aunque los niveles de colesterol de lipoproteínas de baja densidad (LDL-C) deben ser determinados idealmente por betacuantificación o métodos enzimáticos, hay limitaciones en países en vía de desarrollo. El objetivo de este estudio es comparar LDL-C obtenido a través de tres fórmulas (LDL-Cnf) con LDL-C obtenido a través de la fórmula de Friedewald (LDL-Cf) usando LDL-C (LDL-Cr) enzimático considerado como referente más aceptado clínicamente. Métodos: Se realizó un estudio de pruebas diagnósticas en un laboratorio de referencia en Cali, Colombia. Las tres fórmulas fueron (mg/dl): Hombres con triglicéridos menores de 400 mg/dl: LDL-C= Colesterol total (CT) - triglicéridos (TG)/6.5)- 45; hombres con triglicéridos iguales a o mayores de 400 mg/dl: LDL-C= (CT- (TG/7))- 50 y mujeres: LDL-C= (CT- (TG/6.5))- 70. Resultados: Se obtuvieron 315 valores de los cuales 53% eran mujeres. El promedio de edad y LDL-Cr fueron 54 años (±15.8) y 112.1 mg/dl (±32.5), respectivamente. La mediana (rango intercuartil) de CT, lipoproteínas de alta densidad (HDL-C) y TG fueron de 204 mg/dl (171-229), 51 mg/dl (41-61) y 156 mg/dl (99-237), respectivamente. No hubo diferencia en los valores promedio de LDL-Cr y LDL-Cnf (113.48 vs. 112.67 mg/dl; p=0.45). Los coeficientes de correlación intraclase entre LDL-Cr y LDL-Cf y LDL-Cnf fueron altos (r=0.93 y 0.92, respectivamente). La correlación entre LDL-Cf y LDL-Cnf fue de 0.95. No hubo diferencias en las áreas bajo la curvas de características operativas del receptor (COR) con niveles de LDL-Cr de 160 mg/dl (0.94 vs. 093; p=0.27). Conclusión: Existe una alta correlación entre LDL-Cf y LDL-Cnf. Estas formulas podrían ser una alternativa cuando existen limitaciones para determinar el LDL-C.

Comparação analítica de valores de LDL-colesterol utilizando a dosagem direta e o cálculo pela fórmula de Friedewald / Analytical comparison of values of LDL-cholesterol using the direct dosage and the calculation through the formula of Friedewald

A avaliação fidedigna do perfil lipídico dos pacientes é fator fundamental para acompanhamento e prevenção das patologias cardiovasculares. A proposta deste trabalho é avaliar o desempenho de dois métodos para dosagem do LDL-colesterol, um método direto e o método indireto pela fórmula de Friedewald, em uma população heterogênea. Para tal foram realizadas dosagens de triglicerídeos, colesterol total e HDL-colesterol através de métodos enzimáticos tradicionais. Para dosagens de LDL-colesterol foramutilizados os métodos: direto, sem precipitação e o indireto pela estimativa. Os pacientes foram divididos em cinco grupos, de acordocom o resultado das dosagens de triglicerídeos. A estimativa do LDL-colesterol tendeu a mostrar resultados ligeiramente diminuídosem comparação a dosagem pelo método homogêneo para valores de triglicérides inferiores a 70 mg/dL. Entretanto, a estimativa do LDL-colesterol tendeu a produzir resultados significativamente mais elevados, em comparação ao método direto de dosagem, para faixasde triglicérides de 181-290 mg/dL; 291-400 mg/dL e valores superiores a 400 mg/dL. Na faixa de triglicérides de 71-180 mg/dL não houve alteração significativa entre as metodologias empregadas. Este trabalho demonstrou que resultados de LDL-colesterol utilizando a fórmula de Friedewald e a medida direta não são idênticos com diferentes níveis de triglicerídeos.

A worthy evaluation over the lipidic profile of patients is a fundamental factor to the accompaniment and prevention of cardiovascular pathologies. The proposal of this research is to evaluate the performance of two methods of LDL-cholesterol dosage. One is the direct method, and the other is the indirect one which uses the Friedewald's equation, both methods were used on a heterogen population. To make the test there were necessary the dosage of triglycerides, total cholesterol and HDL-cholesterol through traditional enzymatic tests. To the dosage of LDL-cholesterol there were used: the direct method previously said, which is a method without precipitation and the indirect one, that is the method that uses the equation. The patients were divided by five groups, in accordance with their triglyceride dosage results. The indirect method tended to show results slightly diminished in comparison to the dosage through the homogen method to values of triglyceride less than 70 mg/dl. In the other hand the LDL-cholesterol estimative also tends to produce significant higher results in comparison with the direct method. For bands of triglyceride between 181-290mg/dl; 291-400 mg/dl and values greater than 400 mg/dl. In the bands of triglyceride between 71-180 mg/dl there was no significant difference among the two methods. This research showes tha the results of LDL-cholesterol reached through the Friedewald equation and the direct method, are not identical when comparing differents rates of triglyceride.

Comparación entre la determinación analítica del colesterol-LDL y su estimación por cálculo / Comparison between the analytical determination of LDL-cholesterol and its estimation by calculation

El colesterol­LDL (LDL.C) es uno de los principales marcadores de riesgo aterogénico y es utilizado para objetivos preventivos, su determinación por cálculo es frecuente en los laboratorios. Por lo tanto, el objetivo de este estudio fue comparar el método de Friedewal con un método analítico basado en la precipitación de las LDL con sulfato de polivinilo (PVS) descrito por Kerscher. El colesterol ligado a las mismas se determinó empleando el sistema enzimático con colorimetría de Trinder. Por diferencia entre el Colesterol total y el determinado en el sobrenadante, se obtuvo el colesterol unido a las LDL.(C.LDLa). Se comparó con el método por cálculo para la estimación de LDL.C (C.LDLc).Se eliminaron todos los valores de triglicéridos > o = a 400 mg/dl. En los pacientes normolipémicos el valor medio de C.LDLa fue 95 ±29 mg/dl y para C­LDL 99 ±26 mg/dl. El coeficiente de correlación fue r= 0.91 (p< 0.001). En pacientes hipercolesterolémicos, el valor medio de C­LDLa fue 170± 22 mg/dl y para C­LDLc 160 ± 21 mg/dl; el coeficiente de correlación fue r = 0.87 (p< 0.001). En los hipertrigliceridémicos, el valor medio de C­LDLa fue 122 ± 42 mg/dl y para C­LDLc 106 ± 41 mg/dl con coeficiente de correlación r = 0.92 (p< 0.001). En base a estos resultados podemos destacar que el método analítico es rápido, preciso y fácilmente utilizable en el laboratorio clínico y que ambos métodos son comparables entre sí hasta valores de triglicéridos menores a 400 mg/dl.

LDL­cholesterol(LDL­C) is one of the principal markers of atherogenic risk and is used for preventive aims. The determination of this marker by calculation is frequent in laboratories. Thus, the aim of this study was to compare Friedewald formula with an analytical method based on the precipitation of LDL with polyvinyl sulphate (PVS) described by Kerscher. The cholesterol linked to these proteins was determined using the enzymatic colorimetric system of Trinder. The cholesterol linked to LDL (LDL­Ca) was obtained by the difference between total cholesterol and the one determined in the supernatant. This result was compared with the method of calculation for LDL­C estimation. All values of triglycerids > or equal to 400 mg/dl were eliminated. In the normolipemic patients, the mean LDL­Cc was 95 ± 29 mg/dl and for LDL­Cc 99 ± 26 mg/dl. The correlation coefficient was r=0.91 (p <0.001). In hypercholesterolemic patients, mean LDL­Ca was 170 ± 22 mg/dl and for LDL­Cc 160 ± 21 mg/dl; the correlation coefficient was r=0.87 (p <0.001). In hypertriglyceridemic patients, mean LDL­Ca was 122 ± 42 mg/dl and LDL­Cc 106 ± 41 mg/dl with a correlation coefficient of r= 0.92 (p <0.001). Based in these results, we could emphasize that the analytical method is rapid, precise and easy to use in the clinical laboratory and that both methods are comparable for triglyceride values lower than 400 mg/dl.