Cómo estimar la eficacia de un captor del fósforo / How to assess the efficacy of phosphate binders

Antecedentes y objetivos: Es difícil estimar clínicamente la eficacia de los captores de fósforo (CP). Este estudio analiza los cambios que se producen en la fosfatemia y excreción urinaria de fósforo tras la administración de CP a pacientes con enfermedad renal crónica, y la utilidad de la relación entre la excreción urinaria de fósforo y la tasa de catabolismo proteico (Po/TCP) en la estimación de la eficacia de estos fármacos. Métodos: Estudio retrospectivo de observación en una cohorte de pacientes adultos con enfermedad renal crónica en estadios 4-5. Se compararon parámetros bioquímicos basales y 45-60 días después de un tratamiento con dieta baja en fósforo más CP (subgrupo «captor»=260 pacientes) o solo con los consejos dietéticos (subgrupo «control»=79 pacientes). Resultados: La carga de fósforo (excreción urinaria total) por unidad de función renal (Po/GFR) fue el parámetro mejor relacionado con la fosfatemia (R2=0,61). La cifra media de Po/TCP fue de 8,2±2,3mg de fósforo por gramo de proteína. Tras la administración de CP, la fosfatemia descendió un 11%, la fosfaturia un 22%, la tasa de catabolismo proteico un 7% y la Po/TCP un 15%. En el subgrupo control la Po/TCP se incrementó un 20%. La excreción urinaria de fósforo y de nitrógeno ureico se correlacionaron fuertemente de forma lineal antes y después del tratamiento con CP o tras los consejos dietéticos en el subgrupo control. Conclusiones: La Po/TCP es un parámetro que podría reflejar la absorción intestinal de fósforo y, por tanto, sus variaciones tras la administración de CP podrían servir para estimar la eficacia de estos fármacos (AU)

Background and aims: The efficacy of phosphate binders is difficult to be estimated clinically. This study analyzes the changes in serum phosphate and urinary phosphate excretion after the prescription of phosphate binders (PB) in patients with chronic kidney disease stage 4-5 pre-dialysis, and the usefulness of the ratio between total urinary phosphate and protein catabolic rate (Pu/PCR) for estimating the efficacy of PB. Methods: This retrospective observational cohort study included adult chronic kidney disease patients. Biochemical parameters were determined baseline and after 45-60 days on a low phosphate diet plus PB (‘binder’ subgroup=260 patients) or only with dietary advice (‘control’ subgroup=79 patients). Results: Phosphate load (total urinary excretion) per unit of renal function (Pu/GFR) was the best parameter correlated with serum phosphate levels (R2=0.61). Mean±SD level of Pu/PCR was 8.2±2.3mg of urinary phosphate per each g of estimated protein intake. After treatment with PB, serum phosphate levels decreased by 11%, urinary phosphate 22%, protein catabolic rate 7%, and Pu/PCR 15%. In the control subgroup, Pu/PCR increased by 20%. Urinary phosphate and urea nitrogen excretion correlated strongly, both baseline and after PB or dietary advice. Conclusions: The proposed parameter Pu/PCR may reflect the rate of intestinal phosphate absorption, and therefore, its variations after PB prescription may be a useful tool for estimating the pharmacological efficacy of these drugs (AU)

Importancia relativa de los factores determinantes de los niveles séricos de 25-hidroxi-colecalciferol en la enfermedad renal crónica / Relative importance of the determinants of serum levels of 25-hydroxy vitamin D in patients with chronic kidney disease

Introducción: El origen de la carencia de vitamina D en la enfermedad renal crónica (ERC) parece multifactorial, pero es incierta la importancia relativa de cada uno de sus potenciales determinantes. Objetivos: Determinar los factores asociados a los niveles de 25-hidroxi-colecalciferol (25OHD) y su importancia relativa en una cohorte de pacientes con ERC prediálisis. Material y métodos: Se incluyeron pacientes incidentes en una consulta de ERC, excluyendo a aquellos que recibían suplementos de vitamina D o anticonvulsivantes. Además de los datos demográficos y clínicos, se analizó la influencia de la actividad física, estación del año de la extracción, y tratamiento con estatinas, antiangiotensina e inhibidores de la xantino-oxidasa. Para la estimación de la importancia relativa se utilizó el método de ponderación relativa de Johnson, expresando los resultados como porcentajes de contribución al R múltiple. Resultados: Se estudiaron 397 pacientes, de los cuales 30 fueron excluidos. La concentración media de 25OHD fue de 13,7±7,4ng/ml, presentando unos niveles inferiores a 20ng/ml el 81% de los pacientes. Por regresión lineal múltiple y ponderación relativa, los principales determinantes de unos niveles más bajos de 25OHD fueron por orden de importancia: una mayor proteinuria (28,5%), mayor edad (21,4%), disminución de la actividad física (19,4%), sexo femenino (19,3%), y menor bicarbonato sérico (11,4%). Conclusión: La magnitud de la proteinuria y la edad son los factores con mayor importancia relativa como determinantes de los niveles de 25OHD en la ERC (AU)

Introduction: The cause of vitamin D deficiency in chronic kidney disease (CKD) is probably multi-factorial; however, the relative importance of each potential determinant is uncertain. Aims: To determine factors associated with serum levels of 25-hydroxy vitamin D (25OHD) and their relative importance in a cohort of pre-dialysis CKD patients. Material and methods: Incident patients admitted to a CKD outpatient clinic were included. Those who were receiving vitamin D supplements or anticonvulsants were excluded. In addition to demographic and clinical data, information about outdoor physical activity, season of blood collection, prescription of statins, anti-angiotensin drugs and xanthine-oxidase inhibitors were included as potential determinants. Johnson's relative weights analysis was used to estimate the relative importance of each potential determinant and the results were expressed as percentage contribution to multiple R. Results: The study group consisted of 397 patients, 30 of whom were excluded. The mean serum level of 25OHD was 13.7±7.4ng/ml, and 81% of patients had serum levels lower than 20ng/ml. By multiple linear regression and relative weights analyses, the best determinants of low serum 25OHD levels and their relative importance were: higher proteinuria (28.5%), old age (21.4%), low physical activity (19.4%), female gender (19.3%) and low serum bicarbonate levels (11.4%). Conclusions: Proteinuria and age are the determinants with the highest relative importance for predicting 25OHD levels in CKD patients (AU)

Relative importance of the determinants of serum levels of 25-hydroxy vitamin D in patients with chronic kidney disease. / Importancia relativa de los factores determinantes de los niveles séricos de 25-hidroxi-colecalciferol en la enfermedad renal crónica.

INTRODUCTION: The cause of vitamin D deficiency in chronic kidney disease (CKD) is probably multi-factorial; however, the relative importance of each potential determinant is uncertain. AIMS: To determine factors associated with serum levels of 25-hydroxy vitamin D (25OHD) and their relative importance in a cohort of pre-dialysis CKD patients. MATERIAL AND METHODS: Incident patients admitted to a CKD outpatient clinic were included. Those who were receiving vitamin D supplements or anticonvulsants were excluded. In addition to demographic and clinical data, information about outdoor physical activity, season of blood collection, prescription of statins, anti-angiotensin drugs and xanthine-oxidase inhibitors were included as potential determinants. Johnson's relative weights analysis was used to estimate the relative importance of each potential determinant and the results were expressed as percentage contribution to multiple R. RESULTS: The study group consisted of 397 patients, 30 of whom were excluded. The mean serum level of 25OHD was 13.7±7.4ng/ml, and 81% of patients had serum levels lower than 20ng/ml. By multiple linear regression and relative weights analyses, the best determinants of low serum 25OHD levels and their relative importance were: higher proteinuria (28.5%), old age (21.4%), low physical activity (19.4%), female gender (19.3%) and low serum bicarbonate levels (11.4%). CONCLUSIONS: Proteinuria and age are the determinants with the highest relative importance for predicting 25OHD levels in CKD patients.