ABSTRACT
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.
Subject(s)
Humans , Cholesterol, LDL , Outpatients , Epidemiology, Descriptive , Medical Laboratory Science/trends , Observational Study , Regression Analysis , Data Interpretation, StatisticalABSTRACT
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.
Subject(s)
Lipoproteins , Cholesterol, LDL , Secondary CareABSTRACT
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.
ABSTRACT
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)
Subject(s)
Humans , Infant , Child, Preschool , Child , Adolescent , Adult , Cholesterol/blood , Regression Analysis , Clinical Laboratory Techniques/methods , Cholesterol, LDL/blood , Cardiovascular Diseases/prevention & controlABSTRACT
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.
Subject(s)
Humans , Male , Female , Adult , Middle Aged , Laboratory and Fieldwork Analytical Methods/methods , Cholesterol, LDL/analysis , Cholesterol, LDL/blood , Cholesterol, HDL/analysis , Enzymes/blood , Risk Measurement Equipment , Triglycerides/bloodABSTRACT
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.
Subject(s)
Humans , Male , Female , Adult , Middle Aged , Cholesterol , Cholesterol, LDL , TriglyceridesABSTRACT
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.