Performance of creatinine-based equations for estimating glomerular filtration rate compared to endogenous creatinine clearance / Desempenho das equações baseadas em creatinina para estimativa da taxa de filtração glomerular comparadas à depuração da creatinina endógena

Abstract Introduction: The guidelines recommend estimating the glomerular filtration rate using serum creatinine-based equations as a predictor of kidney disease, preferably adjusted for local population groups. Methods: Cross-sectional study that evaluated the performance of four equations used for estimating GFR compared to endogenous creatinine clearance (ClCr) in 1,281 participants. Modification of Diet equations in Renal Disease Study Group (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), CKD-EPI with adjustment for local population (CKD-EPI local) and Full Age Spectrum (FAS) in comparison with endogenous creatinine clearance (ClCr). We used the Quantile Regression to calculate the median bias, interquartile range (IQR), Bland-Altman agreement analysis and 30% margin of error (P30). Results: The mean age of participants was 52.5 ± 16.5 years with 466 women (38%), median ClCr[IQR] of 92.0 [58.0; 122.0] mL/min/1.73 m2, with 320 (25%) participants presenting ClCr < 60 mL/min/1.73 m2. The performance of the local CKD-EPI and FAS equations were superior to MDRD and CKD-EPI in relation to variability (0.92 [0.89; 0.94]) and P30 (90.5% [88.7; 92, 0]). In the group with ClCr < 60 mL/min/1.73 m2, the local CKD-EPI and FAS equations showed less variability than the CKD-EPI and MDRD (0.90 [0.86; 0.98] and 1.05 [0.97; 1.09] vs. 0.63 [0.61; 0.68] and 0.65 [0.62; 0.70], P < 0.01) and best P30 (85.5) % [81.0; 90.0], 88.0% [84.0; 92.0] vs. 52.0% (46.0; 58.0) and 53.0% [47.0; 58 .5], P < 0.01). Conclusion: Local CKD-EPI and FAS equations performed better than CKD-EPI and MDRD when compared to ClCr.

Resumo Introdução: As diretrizes recomendam a estimativa da taxa de filtração glomerular pelo uso de equações baseadas em creatinina sérica como preditor de doença renal, preferencialmente ajustadas para grupos populacionais locais. Métodos: Estudo transversal que avaliou o desempenho de quatro equações para estimativa da TFG em comparação com a depuração de creatinina endógena (DCE) em 1.281 participantes. Foram avaliadas as equações Modification of Diet in Renal Disease Study Group (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), CKD-EPI com ajuste para a população local (CKD-EPI local) e Full Age Spectrum (FAS) em comparação com a depuração de creatinina endógena (DCE). Utilizamos a Regressão Quantílica para cálculo do viés mediano, intervalo interquartil (IQR), análise de concordância de Bland-Altman e margem de erro de 30% (P30). Resultados: A idade média dos participantes era de 52,5 ± 16,5 anos com 466 mulheres (38%), mediana da DCE [IQR] de 92,0 [58,0; 122,0] mL/min/1,73 m2, com 320 (25%) participantes apresentando DCE < 60 mL/min/1,73 m2. A performance das equações CKD-EPI local e FAS foram superiores às MDRD e CKD-EPI em relação à variabilidade (0,92 [0,89; 0,94]) e P30 (90,5% [88,7; 92,0]). No grupo com DCE < 60 mL/min/1,73 m2, as equações CKD-EPI local e FAS apresentaram menor variabilidade que as CKD-EPI e MDRD (0,90 [0,86; 0,98] e 1,05 [0,97; 1,09] vs. 0,63 [0,61; 0,68] e 0,65 [0,62; 0,70], P < 0,01) e melhores P30 (85,5% [81,0; 90,0], 88,0% [84,0; 92,0] vs. 52,0% (46,0; 58,0) e 53,0% [47,0; 58,5], P < 0,01). Conclusão: As equações CKD-EPI local e FAS tiveram desempenho superior às CKD-EPI e MDRD, quando comparadas a DCE.

Association between glomerular filtration rate (measured by high-performance liquid chromatography with iohexol) and plasma oxalate / Associação entre taxa de filtração glomerular (medida por cromatografia liquida de alto desempenho com iohexol) e oxalato plasmático

ABSTRACT Introduction: Secondary hyperoxalemia is a multifactorial disease that affects several organs and tissues in patients with native or transplanted kidneys. Plasma oxalate may increase during renal failure because it is cleared from the body by the kidneys. However, there is scarce evidence about the association between glomerular filtration rate and plasma oxalate, especially in the early stages of chronic kidney disease (CKD). Methods: A case series focuses on the description of variations in clinical presentation. A pilot study was conducted using a cross-sectional analysis with 72 subjects. The glomerular filtration rate (GFR) and plasma oxalate levels were measured for all patients. Results: Median (IQR) GFR was 70.50 [39.0; 91.0] mL/min/1.73 m2. Plasma oxalate was < 5.0 µmol/L in all patients with a GFR > 30 mL/min/1.73m2. Among the 14 patients with severe CKD (GFR < 30 mL/min/1.73 m2) only 4 patients showed a slightly increased plasma oxalate level (between 6 and 12 µmol/L). Conclusion: In non-primary hyperoxaluria, plasma oxalate concentration increases when GFR < 30mL/min/1.73 m2 and, in our opinion, values greater than 5 µmol/L with a GFR > 30 mL/min/1.73 m2 are suggestive of primary hyperoxaluria. Further studies are necessary to confirm plasma oxalate increase in patients with low GFR levels (< 30mL/min/1.73 m2).

RESUMO Introdução: A hiperoxalemia secundária é uma doença multifatorial que afeta vários órgãos e tecidos em pacientes com rins nativos ou transplantados. O oxalato plasmático pode aumentar durante a insuficiência renal porque é eliminado do corpo pelos rins. No entanto, há evidências escassas sobre a associação entre taxa de filtração glomerular e oxalato plasmático, especialmente nos estágios iniciais da doença renal crônica (DRC). Métodos: uma casuística centrada na descrição das variações na apresentação clínica. Foi realizado um estudo piloto a partir da análise transversal com 72 indivíduos. As taxas de filtração glomerular (TFG) e os níveis plasmáticos de oxalato foram medidos para todos os pacientes. Resultados: A TFG mediana (IIQ) foi de 70,50 [39,0; 91,0] mL/min/1,73 m2. O nível plasmático de oxalato foi < 5,0 µmol/L em todos os pacientes com TFG > 30 mL/min/1,73 m2. Entre os 14 pacientes com DRC grave (TFG < 30 mL/min/1,73 m2), apenas quatro apresentaram ligeiro aumento do nível plasmático de oxalato (entre 6 e 12 µmol/L). Conclusão: Na hiperoxalúria não primária, a concentração plasmática de oxalato aumenta quando TFG < 30 mL/min/1,73 m2 e, em nossa opinião, valores superiores a 5 µmol/L com TFG > 30 mL/min/1,73 m2 sugerem presença de hiperoxalúria primária. Estudos adicionais são necessários para confirmar o aumento do oxalato plasmático em pacientes com níveis baixos de TFG (< 30 mL/min/1,73 m2).

Association between arteriovenous fistulae and hematomas in a dialysis center in the state of Rio Grande do Sul, Southern Brazil

Introduction: Chronic kidney disease (CKD) is characterized by slow, progressive, and irreversible loss of kidney function. CKD has become a serious public health issue because of its increasing morbidity and mortality rates. The present study aimed to investigate factors associated with hematomas caused by arteriovenous fistula (AVF) at a Renal Replacement Therapy Unit in the state of Rio Grande do Sul, southern Brazil. Methods: In this cross-sectional study, 72 patients with CKD aged 18 years or over, presenting with AVF, and undergoing three hemodialysis sessions per week were evaluated from June 2014 to March 2015. Prevalence ratios (PRs) with 95% confidence intervals (95% CIs) were estimated for identification of risk factors associated with AVF. P-values < 0.05 were considered significant. Results: Sex, age, self-reported skin color, educational level, hypertension, diabetes, nephrotic syndrome, congestive heart failure, and hepatitis C were not associated with hematoma formation (i.e., all estimated PRs had p-values > 0.05). The single factor associated with hematomas was AVF time shorter than 60 days (PR = 2.04; 95% CI: 1.28-3.27; p < 0.01). Conclusion: AVF maturation time was associated with higher prevalence of hematomas at the cannulation site. Therefore, AVF time should be given special attention in patients undergoing renal therapy at dialysis centers. (AU)