Determination of a new constant to estimate glomerular filtration rate in pediatrics. / Determinación de una nueva constante para la estimación del filtrado glomerular en pediatría.

INTRODUCTION: In pediatrics, glomerular filtration rate (GFR) may be estimated by measured corrected creatinine clearance (mcCrCl) (mL/min/1.73 m2) or the Schwartz formula (eGFR = height/plasma creatinine x k). The constant k depends on the plasma creatinine determination method: k = 0.55 for the Jaffe colorimetric method and k = 0.413 for the enzymatic method. Our laboratory uses the compensated kinetic colorimetric assay (CKC), and differences are observed between the estimated and measured GFR. Hypothesis: The proposed values of k do not adjust to the CKC method for plasma creatinine. OBJECTIVE: To calculate a k value that allows to estimate GFR through creatinine measurement with CKC. METHODS: Correlational, descriptive design. Patients aged 3-18 years seen at the Division of Pediatric Nephrology between July 2017 and January 2018 with normal or altered GFR, bladder and bowel control, and signed consent were included. Malnourished and myelomeningocele patients were excluded. Studied variables were plasma and urine creatinine, height, and 24-hour urine output. RESULTS: A total of 184 patients were analyzed, their mean age was 10 years. Median mcCrCl was 123 mL/min/1.73 m2. The linear correlation between height and plasma creatinine and mcCrCl resulted in a k value of 0.499 (r = 0.974 and r2 = 0.949). The linear correlation between the estimated GFR (k = 0.499) and mcCrCl resulted in a 0.999 ß coefficient (r = 0.951 and r2 = 0.903). CONCLUSION: According to this study, the constant that allows to estimate GFR when measuring plasma creatinine with the CKC method is 0.499.

Introducción. En pediatría, el filtrado glomerular (FG) se puede calcular con el clearance (depuración) de creatinina medida corregida en ml/min/1,73 m2, o se puede estimar según la fórmula de Schwartz (FGe = talla/ creatinina plasmática x k). La constante k depende del método de determinación de creatinina plasmática: k = 0,55 para el método colorimétrico de Jaffe, y k =0,413 para el método enzimático. Nuestro laboratorio utiliza el método colorimétrico cinético compensado (MCCC), se observan discordancias entre el FG estimado y el medido. Hipótesis: Los valores de k propuestos no se ajustan al MCCC de creatinina plasmática. Objetivo. Calcular el valor de k que permita estimar el FG mediante la cuantificación de la creatinina con el MCCC. Métodos. Diseño descriptivo correlacional. Se incluyeron pacientes de entre 3 y 18 años con FG normal o alterado atendidos en el Servicio de Nefrología Infantil entre julio de 2017 y enero de 2018 con control de esfínteres y firma del consentimiento. Se excluyeron pacientes desnutridos y con mielomeningocele. Las variables estudiadas fueron: creatinina plasmática y urinaria, talla y diuresis de 24 horas. Resultados. Se analizaron 184 pacientes, con una edad media de 10 años. La mediana del clearance de creatinina medido corregido fue de 123 ml/ min/1,73 m2. La correlación lineal entre la talla y la creatinina plasmática y el clearance de creatinina medido corregido arrojó un valor de k de 0,499 (r = 0,974 y r2 = 0,949). La correlación lineal entre el FG estimado (k = 0,499) y el clearance de creatinina medido corregido mostró un coeficiente b = 0,999 (r = 0,951 y r2= 0,903). Conclusión. Según este estudio, la constante que permite estimar el filtrado glomerular al cuantificar la creatinina plasmática con el método colorimétrico cinético compensado es de 0,499.

Determinación de una nueva constante para la estimación del filtrado glomerular en pediatría / Determination of a new constant to estimate glomerular filtration rate in pediatrics

Introducción. En pediatría, el filtrado glomerular (FG) se puede calcular con el clearance (depuración) de creatinina medida corregida en ml/min/1,73 m2, o se puede estimar según la fórmula de Schwartz (FGe = talla/creatinina plasmática x k). La constante k depende del método de determinación de creatinina plasmática: k = 0,55 para el método colorimétrico de Jaffe, y k =0,413 para el método enzimático. Nuestro laboratorio utiliza el método colorimétrico cinético compensado (MCCC), se observan discordancias entre el FG estimado y el medido.Hipótesis: Los valores de k propuestos no se ajustan al MCCC de creatinina plasmática. Objetivo. Calcular el valor de k que permita estimar el FG mediante la cuantificación de la creatinina con el MCCC. Métodos. Diseño descriptivo correlacional. Se incluyeron pacientes de entre 3 y 18 años con FG normal o alterado atendidos en el Servicio de Nefrología Infantil entre julio de 2017 y enero de 2018 con control de esfínteres y firma del consentimiento. Se excluyeron pacientes desnutridos y con mielomeningocele. Las variables estudiadas fueron: creatinina plasmática y urinaria, talla y diuresis de 24 horas. Resultados. Se analizaron 184 pacientes, con una edad media de 10 años. La mediana del clearance de creatinina medido corregido fue de 123 ml/min/1,73 m2. La correlación lineal entre la talla y la creatinina plasmática y el clearance de creatinina medido corregido arrojó un valor de k de 0,499 (r = 0,974 y r2 = 0,949). La correlación lineal entre el FG estimado (k = 0,499) y el clearance de creatinina medido corregido mostró un coeficiente b = 0,999 (r = 0,951 y r2= 0,903). Conclusión. Según este estudio, la constante que permite estimar el filtrado glomerular al cuantificar la creatinina plasmática con el método colorimétrico cinético compensado es de 0,499.

Introduction. In pediatrics, glomerular filtration rate (GFR) may be estimated by measured corrected creatinine clearance (mcCrCl) (mL/min/1.73 m2) or the Schwartz formula (eGFR = height/plasma creatinine x k). The constant k depends on the plasma creatinine determination method: k = 0.55 for the Jaffe colorimetric method and k = 0.413 for the enzymatic method. Our laboratory uses the compensated kinetic colorimetric assay (CKC), and differences are observed between the estimated and measured GFR.Hypothesis: The proposed values of k do not adjust to the CKC method for plasma creatinine. Objective. To calculate a k value that allows to estimate GFR through creatinine measurement with CKC. Methods. Correlational, descriptive design. Patients aged 3-18 years seen at the Division of Pediatric Nephrology between July 2017 and January 2018 with normal or altered GFR, bladder and bowel control, and signed consent were included. Malnourished and myelomeningocele patients were excluded. Studied variables were plasma and urine creatinine, height, and 24-hour urine output. Results. A total of 184 patients were analyzed, their mean age was 10 years. Median mcCrCl was 123 mL/min/1.73 m2. The linear correlation between height and plasma creatinine and mcCrCl resulted in a k value of 0.499 (r = 0.974 and r2 = 0.949). The linear correlation between the estimated GFR (k = 0.499) and mcCrCl resulted in a 0.999 ß coefficient (r = 0.951 and r2 = 0.903). Conclusion. According to this study, the constant that allows to estimate GFR when measuring plasma creatinine with the CKC method is 0.499.

Hemolytic uremic syndrome associated with Shiga toxin-producing Escherichia coli infection in Argentina: update of serotypes and genotypes and their relationship with severity of the disease.

BACKGROUND: Shiga toxin-producing Escherichia coli (STEC) infection is the most common cause of hemolytic uremic syndrome (HUS). Only few studies correlated serotypes and stx genotypes with disease severity. This study aimed to update STEC serotypes, stx genotypes, and virulence factors (eae and ehxA) in a cohort of patients with STEC-HUS and investigate whether they influence the severity of disease. METHODS: In this multicentric study, children hospitalized between 2005 and 2016 with STEC-HUS confirmed by the National Reference Laboratory were included. Serotypes (O157, O145, O121, and others), stx genotypes (stx1a, stx2a, stx2c, stx2d, and others), and virulence factors were analyzed, and their association with dialysis requirement (>10 days); severe neurological, cardiovascular, and/or bowel involvement; and death was assessed. RESULTS: The records of 280 patients were reviewed; 160 females, median age 21 months (IQR18m). STEC O157 was isolated in 206 (73.6%) patients, O145 in 47 (16.8%), O121 in 15 (5.4%), and other serotypes in 12 (4.2%). The stx2a/2c genotype was carried by 179 (63.9%) strains, stx2a by 94 (33.6%), stx1a/stx2a by five (1.8%), and stx1a only by two (0.7%). All strains except six harbored eae and ehxA genes. Fifty-nine (21.1%) patients had severe neurological involvement, 29 (10.4%) severe bowel injury, 14 (5%) cardiovascular involvement, 53 (18.9%) required > 10 days of dialysis, and 12 (4.3%) died. Neither serotypes nor stx genotypes detected were significantly linked to severity. CONCLUSIONS: Serotype O157 and virulence stx2a/2c, eae, ehxA genotype are prevalent in Argentina, and no relationship was found between severity and serotypes and genotypes of STEC detected.

Hyponatremia: a new predictor of mortality in patients with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome.

OBJECTIVES: (1) Evaluate mortality rate in patients with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome, (2) determine the leading causes of death, and (3) identify predictors of mortality at hospital admission. METHODS: We conducted a multicentric, observational, retrospective, cross-sectional study. It included patients under 18 years old with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome hospitalized between January 2005 and June 2016. Clinical and laboratory data were obtained from the Argentine National Epidemiological Surveillance System of Hemolytic Uremic Syndrome. Clinical and laboratory variables were compared between deceased and non-deceased patients. Univariate and multivariate analyses were performed. ROC curves and area under the curve were obtained. RESULTS: Seventeen (3.65%) out of the 466 patients died, being central nervous system involvement the main cause of death. Predictors of death were central nervous system involvement, the number of days since the beginning of diarrhea to hospitalization, hyponatremia, high hemoglobin, high leukocyte counts, and low bicarbonate concentration on admission. In the multivariate analysis, central nervous system involvement, sodium concentration, and hemoglobin were independent predictors. The best cut off for sodium was ≤ 128 meq/l and for hemoglobin ≥ 10.8 g/dl. CONCLUSIONS: Mortality was low in children with Shiga toxin-producing Escherichia coli hemolytic uremic syndrome, being central nervous system involvement the main cause of death. The best mortality predictors found were central nervous system involvement, hemoglobin, and sodium concentration. Hyponatremia may be a new Shiga toxin-producing Escherichia coli hemolytic uremic syndrome mortality predictor.