CG Formula Research Articles

Inaccuracies in estimated glomerular filtration rate in one Australian renal centre

Early identification of true renal disease (glomerular filtration rate (GFR) < 60 mL/min) results in better patient outcomes. There is now routine reporting in Australia of estimated GFR (eGFR) in all patients over age 18 who have serum creatinine measured, calculated by the Modification of Diet in Renal Disease (MDRD) formula, which was validated in an American Caucasian cohort. Significant clinical decisions and prognosis are often made on the basis of this calculation. To assess the accuracy of three estimates of GFR in an Australian population by comparing eGFR obtained by the abbreviated MDRD (aMDRD), Cockcroft-Gault corrected for body surface area (BSA) (CG) and Chronic Kidney Disease Epidemiology (CKD-Epi) formulae with a gold standard, isotopic (51) Cr-ethylenediaminetetra-acetic acid ((51) Cr-EDTA) GFR. Patients referred with an eGFR of <60 mL/min reported by the aMDRD formula underwent isotopic measurement of GFR (over 4 h) and had eGFR calculated using CG corrected for BSA, aMDRD and CKD-Epi formulae. Data were analysed using Bland-Altman plots and regression analysis to compare methods; bias, precision and the proportion of patients correctly stratified by stage of chronic kidney disease (CKD) were also compared according to the three estimates of GFR, using (51) Cr-EDTA GFR as the gold standard. A total of 139 patients were recruited (female 45%), mean age 64 years and mean serum creatinine 212 µmol/L. The mean GFR (SD) (mL/min per m(2) ) for isotopic, CG, aMDRD and CKD-Epi were 47 (28), 37 (20), 32 (17) and 33 (18) (P = 0.001). CG (57%) was more likely to correctly stage CKD than aMDRD (37%) or CKD-Epi (37%), and absolute bias was significantly lower using CG than either other method (P = 0.001). In this small Australian population the CG formula corrected for BSA agreed more closely with isotopic GFR and correctly staged patients with CKD more often than the aMDRD or CKD-Epi formulae. It is important that each renal Unit considers the accuracy of estimates of GFR according to their population demographics.

Monitoring of the estimated glomerular filtration rate (eGFR) in patients with small cell lung cancer during chemotherapy: Equations based on serum creatinine or cystatin C?

e19741 Background: Cystatin C (CysC) has been demonstrated as a new marker of glomerular filtration rate. This study compared the differences between eGFR calculated by the Cockcroft&Gault’ (eGFRCG) and CysC-based formula (eGFRCysC) in monitoring renal function in patients with small-call lung cancer (SCLC) during chemotherapy. Methods: Besides the disease-specific parameters, serum creatinine and CysC were detected in 61 patients, and eGFRCG and eGFRCysC after each chemotherapy cycle were calculated and analyzed. Patients also were compared within different eGFR groups. Results: eGFRCysC correlated significantly with serum creatine and eGFRCG respectively (p<0.001). The decreases of eGFRCysC after each treatment cycle were more significant than those decreases of eGFRCG (-3.0634±10.651 vs -0.2274±10.298 ml/min/1.73m2, p=0.001). Single/multi-parameter analysis showed that patients having higher BMI (>23), Scr concentration (>77 μmol/L) and receiving more treatment cycles (>2) were in the increased risk of developing renal impairment with eGFR less than 60 ml/min/1.73 m2 during chemotherapy. Conclusions: The CysC-based formula seems more accurate in predicting eGFR as routine monitoring renal function in patients with SCLC receiving chemotherapy than the CG formula. More attention should be paid to specific patient groups on their renal function during treatment.

Detection and prognostic impact of renal dysfunction in patients with chronic heart failure and normal serum creatinine

Accurate identification of renal dysfunction (RD) is crucial to risk stratification in chronic heart failure (CHF). Patients with CHF are at special risk of having RD despite normal serum creatinine (SCr), owing to a decreased Cr generation. At low levels of SCr, the equations estimating renal function are less accurate. This study was aimed to assess and compare the prognostic value of formulas estimating renal function in CHF patients with normal SCr. We studied 462 patients with systolic CHF and normal SCr. Creatinine clearance was estimated by the Cockcroft-Gault (eCrCl) and glomerular filtration rate by the 4-variable MDRD equation (eGFR); eCrCl normalized for body-surface area (eCrCl(BSA)) was calculated. The primary outcome was all-cause mortality at 2 years. Seventy five patients died. At multivariate Cox regression analysis, only eCrCl(BSA) was significantly associated with mortality (p = 0.006); eGFR (p = 0.24), eCrCl (p = 0.09) and BUN (p = 0.14) were not statistically significant predictors. The patients in the lowest eCrCl(BSA) quartile had an adjusted 2.1-fold (CI: 1.06-4.1) increased risk of mortality, compared with those in the referent quartile. Two-year survival was 70.4% in the lowest eCrCl(BSA) quartile and 89.7% in the referent quartile. Other independent predictors of mortality were ischemic etiology (RR: 2.16 [CI: 1.3-3.5], p = 0.0017), NYHA III/IV class (RR: 2.45 [CI: 1.51-3.97], p = 0.0003), LVEF <0.25 (RR: 3.38 [CI: 1.69-6.75], p = 0.014), and anemia (RR: 1.86 [CI: 1.16-2.99], p = 0.009). A sizeable proportion of CHF patients have prognostically significant RD despite normal SCr. Such patients represent a high-risk subgroup and can more accurately be identified by the CG formula corrected for BSA than the MDRD.

Estimation of the Glomerular Filtration Rate Through Different Methods in Kidney Transplant Recipients: Correlation With the Creatinine Clearance Measurement

The measurement of the glomerular filtration rate (GFR) is an important tool for physicians to follow kidney transplant recipients. Indeed, renal function has been shown to be predictive of graft outcome in retrospective studies. Several methods have been proposed to measure GFR. In the present study we evaluated the correlation of GFR between a reference method (calculation through the urine to plasma ratio of creatinine [UV/P] formula) and three estimation equations (Cockcroft and Gault; Nankivell; modification of diet in renal disease) in 81 kidney transplant recipients at 3 and 12 months posttransplantation. We showed a significant correlation between the three predictive formulas and UV/P, but none of the predictive equations showed an excellent correlation. The best correlation between an estimation equation and the UV/P formula was the CG formula. Further studies are required to compare the estimated GFR with better reference methods, such as the use of isotopic markers in kidney graft recipients.

Glucose Control Influences Glomerular Filtration Rate and Its Prediction in Diabetic Subjects

Hyperglycemia increases glomerular filtration rate (GFR), but the influence of HbA(1c) (A1C) on GFR and GFR's prediction by recommended equations remains to be determined. In 193 diabetic patients, we searched for an association between A1C and isotopically measured GFR (51Cr-EDTA) and their predictions by the Cockcroft and Gault formula (CG) and the modification of diet in renal disease (MDRD) equation. Their accuracy for the diagnosis of moderate (GFR <60 ml/min per 1.73 m(2)) or severe (GFR <30 ml/min per 1.73 m(2)) renal failure was compared from receiver operating characteristic (ROC) curves, before and after categorizing the patients as well (A1C <or=8%) or poorly controlled. The mean GFR was 57.0 +/- 34.8 ml/min per 1.73 m(2) and was well correlated with both estimations (CG r = 0.75, MDRD r = 0.83; P < 0.05). The areas under the ROC curves were higher with the MDRD (P < 0.05). A1C was correlated (P < 0.001) with the GFR (r = 0.29), MDRD (r = 0.38), CG (r = 0.26), and the absolute differences between the GFR and their CG but not MDRD estimations (r = 0.17, P < 0.05). Each +1% A1C was associated with +6.0 ml/min per 1.73 m(2) GFR (CG +5.6, MDRD +5.3). After separating well-controlled (n = 88, A1C 7.0 +/- 0.7%) and poorly controlled (n = 105, 9.6 +/- 1.3%) patients, the diagnostic accuracies were better (P < 0.05) for the MDRD, except for the diagnosis of moderate renal failure in well-controlled patients (NS). GFR and its estimations correlate with A1C. Although the relations between GFR and its estimations were not affected by the degree of glucose control, the precision and diagnostic accuracy of the CG formula were diminished for A1C >8%. The MDRD equation was more accurate and robust in diabetic patients with impaired renal function.

Bedside Estimation of the Glomerular Filtration Rate in Hospitalized Elderly Patients

Aims: To evaluate the quality of bedside estimation of glomerular filtration rate (GFR) in hospitalized elderly patients. Methods: We evaluated common estimators of GFR in 29 women and 32 men aged 60 and older hospitalized in a geriatric ward: creatinine clearance (CCR), the Cockcroft-Gault formula (CG), the modification of diet in renal disease formula (MDRD), Baracskay formula (BAR), and a newly developed formula derived recently by us (GCM). Inulin clearance (CINU) was used to assess GFR. Exclusion criteria were mental illness and urinary incontinence. Results: According to Bland and Altman accuracy and precision of all estimators were low and there was an underestimation of actual GFR: CCR 38.9 ml/min; CG 39.7 ml/min; MDRD 19.8 ml/min; BAR 34.0 ml/min, and GCM: 24.7 ml/min. The accuracy and precision of all methods were even lower in patients with a GFR of >90 ml/min and in patients with diabetes. In receiver-operating characteristics (ROC analysis) all formulas were superior to serum creatinine and overall MDRD disclosed the best results in detecting both a GFR of <90 ml/min and <60 ml/min. Conclusions: In general, estimation errors are large in an acute care setting. However, formula estimation is clearly superior to serum creatinine and CCR. MDRD gave the best results but may be replaced by the more simple CG and GCM formulas, whereas BAR was inferior.

A CALCINEURIN-INHIBITOR FREE PROTOCOL FOR RENAL TRANSPLANTATION IN AN “OLD FOR OLD” ALLOCATION: TWO YEAR RESULTS

P225 The ever growing number of so called marginal donors (MDs) and the elderly uremics request for graft are features of today scenario of renal transplantation. The policy of an “old for old” allocation – i.e. offering kidneys from MDs to elderly candidates – seems to fit well with this condition, as well as to enhance a maximal kidney utilization. Aims: aim of the study is to present the two year results of a protocol we adopted in our Centre in order to avoid the nephrotoxic effect of calcineurin-inhibitors (CNIs) whose impact could be magnified in the milieu of elderly candidates. This protocol is a two-phases immunosuppression, initially CNI free. Methods: the protocol consists of an induction phase with basiliximab 2 doses iv, steroid and mycophenolate mofetil (MMF) 2gr/day and of a maintenance phase with CNI (mainly tacrolimus) when serum creatinine (sCr) is below 2.5 mg/dl. From this time MMF is rapidly stopped and steroid is tapered to 5 mg at day 45, with the aim of minimization/withdrawal. MDs are defined on the basis of clinical (age > 50 years, presence of comorbid conditions), histological (Karpinsky score on harvesting time biopsies) and functional (Cockroft-Gault formula = CG) criteria. Kidneys from 89 MDs were transplanted as single (n=43) or dual (n=46) grafts (G1). 38 grafts from MDs at a lesser degree of marginality rate, CNI treated from day 1, were used as control group (G2). Mean follow up was: 22.5±10.5 months in G1 and 26.1±15.9 months in G2. Results delayed graft function (DGF) rate is statistically higher in G1: 46% vs 27%. Overall patient and graft survival at 12-24 months were:100-97% and 96-91% in G1; 94-94% and 88-88% in G2. As for biopsy proven acute rejection (AR) rates: overall 12.4% (G1), 13.0% (G2); at month 1: 7.0% (G1), 8.8% (G2). AR was the cause for graft loss in 2/89 in G1 and 1/38 in G2. sCr and clearance (CG formula) at 6, 12 and 24 months were respectively in G1: 1.6±0.5, 1.6±0.5, 1.5±0.5 mg/dl and 48±19, 48±18, 52±18 cc’; in G2: 1.6±0.6, 1.7±0.7, 1.7±0.8 mg/dl and 55±19, 56±23, 61±29 cc’. After 2 years, 70% of the patients in G1 and 50% in G2 were off steroids. No significant difference was found between the two groups for all these data. Conclusions: our results give support to the ongoing adoption of a CNI free protocol for grafts harvested from MDs, on the basis of its safety and effectiveness in recipients whose DGF rate and risk factors for nephrotoxicity are both high. The feasibility on an “old for old” transplantation program may help in counteracting the effect of organ shortage.