Ariana Aguiar Soares

Glomerular filtration rate measurement and prediction equations.

Abstract Chronic kidney disease (CKD) is defined as the presence of kidney damage or a glomerular filtration rate (GFR) <60 mL/min/1.73 m2 for three or more months. Measurement of serum creatinine is the most commonly used method to evaluated kidney function, but it must be included in formulas to estimate GFR, adjusting for age, gender and ethnicity, such as the Modification of Diet in Renal Disease (MDRD) study equation. The performance of this equation is acceptable for patients with CKD but appears to under-estimate GFR in populations with unknown kidney status. A new formula has been developed recently. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation appears to perform better than the MDRD equation. Cystatin C has been widely evaluated as a marker for GFR and seems to be more sensitive than creatinine. The aim of this review is to discuss the recommendations for detecting CKD, emphasizing the characteristics and limitations of GFR estimating equations and pitfalls in the evaluation of urinary albumin excretion. Clin Chem Lab Med 2009;47:1023–32.

Comparison between IDMS-traceable Jaffe and enzymatic creatinine assays for estimation of glomerular filtration rate by the CKD-EPI equation in healthy and diabetic subjects.

OBJECTIVES The aim of this paper was to compare the agreement between creatinine measured by Jaffe and enzymatic methods and their putative influence on eGFR as calculated by the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation in healthy and diabetic individuals. DESIGN AND METHODS Cross-sectional study conducted in 123 adult southern Brazilians with GFR>60 mL/min/1.73 m² (53 patients with type 2 diabetes, 70 healthy volunteers). Mean age was 49±16 years (range of 19-86). Most were female (55%) and white (83%). Creatinine was measured by a traceable Jaffe method (Modular P, Roche Diagnostic) and by an enzymatic method (CREA plus, Roche/Hitachi 917). GFR was measured by the ⁵¹Cr-EDTA single-injection method. RESULTS Serum creatinine measured by the Jaffe and enzymatic methods was similar in healthy subjects (0.79±0.16 vs. 0.79±0.15 mg/dL, respectively, P=0.76), and diabetic patients (0.96±0.22 vs. 0.92±0.29 mg/dL, respectively, P=0.17). However, the correlation between the two methods was higher in the healthy group (r=0.90 vs. 0.76, P<0.001). The difference between Jaffe creatinine and enzymatic creatinine was <10% in 63% of cases in the healthy group and 40% of cases in the diabetes group (P=0.018). In the subset of patients with diabetes, eGFR based on enzymatic assay results showed better agreement with measured GFR than did eGFR based on Jaffe results. CONCLUSION Jaffe and enzymatic creatinine methods show adequate agreement in healthy subjects, but in the presence of diabetes, the enzymatic method performed slightly better.

Glomerular filtration rate estimation: performance of serum cystatin C-based prediction equations.

Abstract Serum creatinine measurement is a mainstay in the routine laboratory evaluation of renal function, despite of having several disadvantages. Cystatin C, on the other hand, suffers less influence of gender and muscle mass and has been proposed as a more sensitive marker for glomerular filtration rate. However, serum endogenous markers should not be used alone to assess glomerular filtration rate. Creatinine-based equations such as the modification of diet in renal disease (MDRD) and Cockcroft-Gault are widely used despite their limitations. A large number of cystatin C-based prediction equations were developed in recent years, in diverse populations, with different laboratory assays and methods. Several studies demonstrated that cystatin C-based equations are reliable markers of glomerular filtration rate and can be used for diagnosis, evaluation and follow-up of kidney disease. They are simpler than creatinine-based equations and have at least the same accuracy and precision for glomerular filtration rate estimation. In conclusion, diabetes mellitus, cystic fibrosis, kidney transplantation, HIV-infection, and cirrhosis are clinical situations where cystatin C-based equations can be useful. Extremes of age such as childhood and advanced age have also been evaluated with favorable results.

Performance of CKD-EPI equation to estimate glomerular filtration rate as compared to MDRD equation in South Brazilian individuals in each stage of renal function

Abstract Background: The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation seems to correct the overdiagnosis of chronic kidney disease (CKD) provided by Modification of Diet in Renal Disease (MDRD) equation. However, this point has not been tested in some ethnic groups. This study investigated the performance of MDRD and CKD-EPI equations in South Brazilian individuals. Methods: This cross-sectional study included 354 individuals including healthy volunteers, diabetic and non-diabetic individuals with or without CKD. Glomerular filtration rate (GFR) was measured by the 51Cr-EDTA single-injection method (51Cr-GFR). Accuracy (P30), bias, and Bland-Altman agreement plots were evaluated. Results: In the group as a whole, 51Cr-GFR was 87±37 (6-187), CKD-EPI eGFR, 82±30 (6-152), and MDRD eGFR, 77±28 (6-156) mL/min/1.73 m2 (p<0.001 for all comparisons). Analyzing the subset of individuals with 51Cr-GFR <60 mL/min/1.73 m2, P30 values were, respectively, 76% and 84% for MDRD and for CKD-EPI (p<0.001) while for 51Cr-GFR ≥60 mL/min/1.73 m2, P30 values were 57.5% for both equations (p=1.000). For MDRD and CKD-EPI, mean bias were negative for GFRs <60 (–11 vs. –12, p=0.221) and positive for values >60 (16 vs. 9, p<0.001). In multivariate analysis, absolute bias was unfavorably influenced by measured GFR >60 (for MDRD) and being diabetic or younger (for CKD-EPI). Conclusions: CKD-EPI reduces GFR underestimation in individuals with GFRs >60, but still presents a quite low accuracy at this GFR range. Moreover, it tends to overestimate GFR in subjects with GFRs <60 mL/min/1.73 m2. CKD stages 1 and 2, diabetes and young age had a negative influence on the performance of the equations.

Reference values for glomerular filtration rate in healthy Brazilian adults

BackgroundGlomerular filtration rate (GFR) is the best index of renal function, but age, gender and ethnicity can putatively affect its values. The aim of this study was to establish reference values for GFR in healthy Brazilian subjects while taking these factors into account.MethodsIn this cross-sectional study, GFR was measured by the 51Cr-EDTA single-injection method. GFR reference values were developed according to CLSI Guidelines for Defining, Establishing, and Verifying Reference Intervals in the Clinical Laboratory (CLSI C28 protocol).ResultsThe age range of the 285 healthy individuals was 19 to 70 years, 57% were females, and GFR was 106 ± 18 mL/min/1.73 m2. There was no difference between male and female GFRs (108 ± 18 vs. 104 ± 18 mL/min/1.73 m2 respectively, P = 0.134), and reference values were therefore developed from the pooled sample. GFR values were lower in subjects aged ≥45 years as compared with those younger than 45 years (98 ± 15 vs.112 ± 18 mL/min/1.73 m2, P < 0.001). Based on mean ± 2 SD, GFR reference values were 76 to 148 mL/min/1.73 m2 for subjects younger than 45 years and 68 to 128 mL/min/1.73 m2 for individuals older than 45 years, irrespective of gender.ConclusionThe age-adjusted reference intervals reported may be reliably adopted to evaluate kidney function, since they are based on recommended standards.

Influence of age, gender and body mass index on late-night salivary cortisol in healthy adults

Abstract Background: Late-night salivary cortisol (LNSC) is one of the most reliable tests to screen for endogenous Cushing syndrome. This test is simple, inexpensive and noninvasive and has high sensitivity and specificity. The aim of our study was to analyze the putative influence of age, gender and body mass index (BMI) on LNSC levels in a healthy population. Methods: Cross-sectional study conducted in healthy adults. Midnight saliva samples were collected at home. Participants refrained from teeth brushing, eating or drinking for 2 h prior to collection. Salivary cortisol measured by electrochemiluminescence immunoassay (ECLIA). The study was approved by the Ethics Committee of the hospital (number 140073). Results: We evaluated 122 nonsmoking healthy volunteers. Mean age was 35±14 years (range, 18–74 years); 63% were women. Mean BMI was 24±3 kg/m2, blood pressure 115/74 mmHg and fasting plasma glucose 4.8±0.5 mmol/L. LNSC presented a non-Gaussian distribution; the median was 3.58 (range, 0.55–8.55) nmol/L (0.13 [range, 0.02–0.31] μg/dL), and the 97.5th percentile (P97.5) was 8.3 nmol/L (0.3 μg/dL). Multiple linear regression disclosed a significant positive association between salivary cortisol levels and age (r2=0.21, p<0.001), but no association with gender (p=0.105) or BMI (p=0.119). Accordingly, participants aged >50 years had significantly higher salivary cortisol as compared to those aged <50 years (5.24 nmol/L [0.19 μg/dL] vs. 3.31 nmol/L [0.12 μg/dL], respectively, p<0.001). Conclusions: The maximum reference value (P97.5) of LNSC was set at 8.3 nmol/L (0.3 μg/dL) using ECLIA. Advanced age was associated with higher LNSC levels, with no evident influence of gender or BMI.

Low rates of automatic reporting of estimated glomerular filtration rate in Southern Brazilian laboratories

OBJECTIVES The aim of this study was to evaluate the rate of eGFR reporting in Southern Brazilian laboratories. DESIGN AND METHODS The eGFR automatic reporting, as assessed by Modification of Diet in Renal Disease (MDRD) and/or Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine-based equations, was evaluated in a representative cross-sectional sample. A standardized questionnaire to obtain this information was given out by mail or email. RESULTS Five-hundred fifty laboratories, evenly distributed in the different state regions, completed the questionnaire. The eGFR was automatically reported by 54 (9.8%) laboratories, and the MDRD was the most commonly used equation (94.5%). The Jaffe methods were the most employed technique (94%) to measure serum creatinine. CONCLUSION The automatic eGFR reporting rate was unacceptably low, emphasizing the crucial role of educating medical teams and laboratories on the importance of having these tools available to optimize detection of renal disease and proper treatment.

Combined creatinine-cystatin C CKD-EPI equation significantly underestimates measured glomerular filtration rate in people with type 2 diabetes mellitus

AIM To evaluate the accuracy of creatinine and cystatin C (cysC) equations to estimate glomerular filtration rate (GFR) in type 2 diabetes mellitus (DM) patients and healthy adults. METHODS Case-control study including 84 patients with type 2 DM and 100 healthy adults with measured GFR (mGFR)≥60mL/min/1.73m2. GFR was measured by 51Cr-EDTA and estimated (eGFR) by the following equations using creatinine, cysC or both markers: Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), Caucasian Asian Pediatrics and Adults (CAPA), CKD-EPI creatinine-cystatin C (CKDEPI-CC), and CKD-EPI cystatin C (CKDEPIcysC). Agreement was evaluated by Bland & Altman analysis. RESULTS Healthy individuals were 66% females, aged 38±14years; they presented mGFR 112±19mL/min/1.73m2 and eGFR by CKD-EPI, CKDEPI-CC, CKDEPIcysC and CAPA equations, respectively, 108±17, 102±15, 97±16 and 93±16mL/min/1.73m2. DM group were 50% females, aged 59±19years and presented mGFR 104±27 and eGFR 87±19, 80±18, 74±20 and 73±18mL/min/1.73m2, respectively. All equations significantly underestimated mGFR, excepting creatinine-based CKD-EPI in the healthy group. The performance was considerably worse for GFRs above 120mL/min/1.73m2. CONCLUSION In both healthy and type 2 DM patients, cystatin C-based equations, including the combined CKD-EPI creatinine-cystatin equation, failed to improve the accuracy of GFR estimation, especially for normal and high normal GFR values.

Determinants of glycemic and blood pressure control in type 2 diabetes patients: 606 outpatients diabetes cohort.

Materials and methods 606 type 2 diabetes patients, outpatient Endocrine clinic, tertiary hospital, consecutively included between 20122014. Medical history, complete examination and laboratory evaluation performed (HbA1c, lipids, glomerular filtration rate -eGFRand urinary albumin excretion-UAE). Therapeutic targets defined according to American Diabetes Association: HbA1c <7% (<8% if comorbidities); blood pressure <140/90 mmHg, total cholesterol (TC) <200 mg/dL, HDL adjusted for gender and triglycerides (TG) <150 mg/dL. Approved by ethics committee (no 140073); statistical analysis PASW 20.0.