Estimation of glomerular filtration rates before and after orthotopic liver transplantation: evaluation of current equations

Chronic kidney disease after orthotopic liver transplantation: impact of hepatitis C infection

BACKGROUND

Hepatitis C virus (HCV) infection has been shown to be a potential risk factor for the development of chronic kidney disease in liver transplant recipients.

METHODS

We performed a retrospective cohort study of 307 patients with and without HCV cirrhosis and preserved pretransplant renal function (serum creatinine<1.5 mg/dL pretransplantation) to assess the impact of HCV on the incidence of posttransplant chronic kidney disease. Kaplan-Meier analysis was performed for time to development of estimated glomerular filtration rate (eGFR) less than 30 mL/min, need for dialysis, and mortality.

RESULTS

One hundred eighty-one patients were transplanted for HCV cirrhosis and 126 recipients had other causes of liver disease. Mean model for end-stage liver disease scores were 21.64 in the HCV group and 21.30 in the non-HCV group (P=0.58); 51% of patients in the HCV cohort had hepatocellular carcinoma compared with 27% in the non-HCV cohort (P<0.001). Mean pretransplant serum creatinine level was 0.89 mg/dL in both groups. At 3 years posttransplant, eGFR did not differ between the HCV and non-HCV cohorts (64.96 mL/min vs. 66.09 mL/min; P=0.71). A total of 14.4% of the patients with HCV achieved an eGFR less than 30 mL/min compared with 10.3% of the patients without HCV (P=0.13). There was no difference between the cohorts with respect to requirement for dialysis (P=0.73) or deaths (P=0.08), including those that were liver related (P=0.15).

CONCLUSIONS

Patients with HCV cirrhosis and normal preliver transplant renal function do not have worse posttransplant renal outcomes compared with those with other causes of liver disease.

Basiliximab induction and delayed calcineurin inhibitor initiation in liver transplant recipients with renal insufficiency

BACKGROUND

Renal insufficiency (RI) is common after liver transplantation (LT) and may worsen due to calcineurin inhibitor (CNI) use. We compared LT outcomes using basiliximab induction and delayed CNI initiation to controls with a standard CNI regimen in patients with peri-LT RI.

METHODS

All adults transplanted January 2004 to December 2007 with peri-LT RI (hemodialysis or creatinine ≥1.5 within 1 week of LT) were included in a retrospective nonrandomized cohort. Outcomes including 30-day and 1-year patient and graft survival and renal function were compared between basiliximab and control groups.

RESULTS

Two hundred twenty-nine patients (102 basiliximab, 127 controls) were analyzed, mean age 54 years, 72% men, 54% with hepatitis C virus. Mean model for end-stage liver disease (28.2 vs. 20.0; P<0.001) and creatinine (1.9 vs. 1.6; P=0.001) were higher and more patients were on hemodialysis at LT (29% vs. 6%; P<0.001) in the basiliximab group. 30-day patient (99% vs. 97%; P=0.26) and graft survival (98% vs. 95%; P=0.17), 1-year patient (87% vs. 87%; P=0.89) and graft survival (86% vs. 82%; P=0.37), mean creatinine at 1-year (1.5 vs. 1.5 mg/dL; P=0.82), and treated acute rejection (6% vs. 6%; P=0.90) were similar between basiliximab and control groups, respectively. In multivariable logistic regression, basiliximab was not significantly associated with 30-day (odds ratio, 0.10; P=0.11) or 1-year (odds ratio, 0.97; P=0.94) survival, controlling for age, previous LT, model for end-stage liver disease, and hepatitis C virus.

CONCLUSIONS

Basiliximab induction resulted in 30-day and 1-year patient, graft and renal outcomes comparable with a control group receiving standard CNI-based immunosuppression. Antibody induction with delayed CNI should be further studied prospectively.

Pitfalls in assessing renal function in patients with cirrhosis--potential inequity for access to treatment of hepatorenal failure and liver transplantation

Serum creatinine is universally used to assess renal function in clinical practice. Creatinine and changes in serum creatinine are used to define acute kidney injury and hepatorenal syndrome (HRS) in patients with progressive liver disease. In addition, creatinine is a key variable in the calculation used to determine priority for liver transplantation in many countries. As there is no universal standardized creatinine assay, there is variation in creatinine determinations between laboratory assays, compounded by assay interference due to chromogens, including bilirubin. This leads to patients with the same actual renal function potentially being offered different treatment options, in terms of access to therapy for HRS and priority waiting time for liver transplantation. Alternative methods for assessing renal function either also tend to overestimate renal function or are too time consuming and expensive to provide practical alternatives for standard clinical practice. Standardization of creatinine assays with readily available reference standards would help minimize interlaboratory variation; of the current creatinine assays, enzymatic creatinine appears more accurate, but even this is inaccurate at high bilirubin concentrations. Further work is required to determine whether interpatient variation can be reduced by correcting creatinine and cystatin measurements for muscle mass.

Chronic kidney disease following liver transplantation: a South Australian experience

The incidence of chronic kidney disease (CKD) and its impact on survival have not been widely studied in the Australian liver transplant (OLT) population. The aims of this study were to evaluate the prevalence of CKD stages at various time points, calculate the cumulative incidence of progression to severe CKD, and study the impact of CKD stages on patient survival and risk factors for severe CKD in a single-center post-OLT population. We studied retrospectively 130 patients who underwent OLT in South Australia with a minimum of 6 months of follow-up from 1992 to 2008. CKD was staged according to Kidney Diseases Outcome Quality Initiative Guidelines. Glomerular filtration rate (GFR) was calculated using the Modification of Diet in Renal Disease equation. Multiple pre- and post-OLT variables were examined for their association with severe CKD. Log-rank tests and Cox regression analysis were performed to evaluate the survival data. The cumulative incidences of severe CKD (stages 4 and 5) at 2, 5, and 15 years were 3.8%, 12.7%, and 14.8%, respectively. Severe CKD was associated with an increased mortality (hazard ratio 6.5; 95% confidence interval = 2.5-17.0; P < .001). Mild and moderate CKD stages were not associated with increased mortality. Risk factors for severe CKD were: female gender, hepatitis C infection, pre-OLT diabetes, acute renal failure post-OLT, and low 1-year GFR. Mild and moderate CKD are common post-OLT. The development of severe CKD, which can be predicted early in the post-OLT period, is strongly associated with an increased mortality rate.

Gender, renal function, and outcomes on the liver transplant waiting list: assessment of revised MELD including estimated glomerular filtration rate

BACKGROUND & AIMS

The Model for End-Stage Liver Disease (MELD) allocation system for liver transplantation (LT) may present a disadvantage for women by including serum creatinine, which is typically lower in females. Our objectives were to investigate gender disparities in outcomes among LT candidates and to assess a revised MELD, including estimated glomerular filtration rate (eGFR), for predicting waiting list mortality.

METHODS

Adults registered for LT between 2002 and 2007 were identified using the UNOS database. We compared components of MELD, MDRD-derived eGFR, and the 3-month probability of LT and death between genders. Discrimination of MELD, MELDNa, and revised models including eGFR for mortality were compared using c-statistics.

RESULTS

A total of 40,393 patients (36% female) met the inclusion criteria; 9% died and 24% underwent LT within 3 months of listing. Compared with men, women had lower median serum creatinine (0.9 vs. 1.0 mg/dl), eGFR (72 vs. 83 ml/min/1.73 m(2)), and mean MELD (16.5 vs. 17.2; all p <0.0005), but within most MELD strata, had higher bilirubin and INR. After adjusting for relevant covariates including creatinine and body weight, women were less likely than men to receive a LT (hazard ratio [HR] 0.85; 95% CI 0.79-0.87) and had greater 3-month mortality (HR 1.13; 95% CI 1.05-1.21). Revision of MELD and MELDNa to include eGFR did not improve discrimination for 3-month mortality (c-statistics: MELD 0.896, MELD-eGFR 0.894, MELDNa 0.911, MELDNa-eGFR 0.905).

CONCLUSIONS

Women are disadvantaged under MELD potentially due to its inclusion of creatinine. However, since including eGFR in MELD does not improve mortality prediction, alternative refinements are necessary.

Is estimated glomerular filtration rate superior to serum creatinine in predicting mortality on the waiting list for liver transplantation?

Serum creatinine is an important prognostic indicator in patients on the liver transplant waiting-list, being a component of the Model for End Stage Liver Disease (MELD) score. However, creatinine is influenced by age, gender and race, and in this role may disadvantage some individuals. The Modification of Diet in Renal Disease (MDRD) estimated glomerular filtration rate (eGFR) takes into account these variables and may be a superior measure of renal function. Our aim was to examine whether the MDRD 4-variable, 5-variable and 6-variable eGFRs are superior to serum creatinine in predicting 3-month waiting-list mortality in patients with end-stage liver disease. This was a retrospective single-centre study of 427 adults listed for first liver transplantation. The median listing MDRD 4-variable, 5-variable and 6-variable eGFR was 69, 71 and 73 ml/min/1.73 m(2) , respectively. The median listing serum creatinine was 89 μm. MDRD 4-variable (P = 0.002), 5-variable (P < 0.001) and 6-variable eGFR (P < 0.001), and serum creatinine (P < 0.001), were all predictors of mortality on the transplant waiting-list. Of the three MDRD equations, the 6-variable eGFR was the better prognostic indicator. The substitution of 6-variable eGFR for serum creatinine did not improve the prognostic accuracy of the MELD (P = 0.825) and UK score for Patients with End-Stage Liver Disease (P = 0.781) scores. In conclusion the MDRD eGFR is comparable, but not superior to serum creatinine, in predicting death within 3 months of listing for liver transplantation.

Assessing creatinine clearance from modification of diet in renal disease study equations in the ADEMEX cohort: limitations and potential applications

BACKGROUND AND OBJECTIVES

Twenty-four-hour urine and dialysate collections provide accepted means to assess adequacy in peritoneal dialysis (PD). Recent publications suggest that creatinine clearance (CrCl) estimated from the Modification of Diet in Renal Disease (MDRD) equations (eCrCl) accurately approximates measured CrCl (mCrCl) derived from 24-hour collections of urine and dialysate and might serve as an alternative means to assess small-solute clearance and adequacy in PD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Post hoc analysis of data from patients enrolled in ADEMEX was used to assess agreement between mCrCl and eCrCl derived by four- and six-variable MDRD equations (4V-MDRDE and 6V-MDRDE, respectively). Additionally, associations among mCrCl, eCrCl, and survival were determined.

RESULTS

Acceptable precision was observed between mCrCl and 4V-MDRDE-eCrCl and 6V-MDRDE-eCrCl for the entire cohort. Precision was markedly diminished when analysis was limited to functionally anuric patients with mCrCl < 12 ml/min per 1.73 m². Although there was no association between survival and mCrCl, for every 1-ml/min per 1.73 m² increase in 4V- and 6V-MDRDE-eCrCl, there was a 6% and 4% increase in risk of death, respectively. There was a negative association between MDRDE-eCrCl and creatinine appearance rates, suggesting MDRDE-eCrCl is significantly confounded by individual differences in muscle mass.

CONCLUSIONS

MDRDE-eCrCl provides demographically comparable values to 24-hour urine and dialysate collections across the ADEMEX cohort. However, MDRDEs should not be used to assess small-solute removal or adequacy in individual PD patients or to predict outcome in any cohort of patients over narrow ranges of limited clearance.

Evaluation of the Chronic Kidney Disease Epidemiology Collaboration equation for estimating the glomerular filtration rate in multiple ethnicities

An equation from the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) provides more accurate estimates of the glomerular filtration rate (eGFR) than that from the modification of diet in renal disease (MDRD) Study, although both include a two-level variable for race (Black and White and other). Since creatinine generation differs among ethnic groups, it is possible that a multilevel ethnic variable would allow more accurate estimates across all groups. To evaluate this, we developed an equation to calculate eGFR that includes a four-level race variable (Black, Asian, Native American and Hispanic, and White and other) using a database of 8254 patients pooled from 10 studies. This equation was then validated in 4014 patients using 17 additional studies from the United States and Europe (validation database), and in 1022 patients from China (675), Japan (248), and South Africa (99). Coefficients for the Black, Asian, and Native American and Hispanic groups resulted in 15, 5, and 1% higher levels of eGFR, respectively, compared with the White and other group. In the validation database, the two-level race equation had minimal bias in Black, Native American and Hispanic, and White and other cohorts. The four-level ethnicity equation significantly improved bias in Asians of the validation data set and in Chinese. Both equations had a large bias in Japanese and South African patients. Thus, heterogeneity in performance among the ethnic and geographic groups precludes use of the four-level race equation. The CKD-EPI two-level race equation can be used in the United States and Europe across a wide range of ethnicity.

Inaccuracies of creatinine and creatinine-based equations in candidates for liver transplantation with low creatinine: impact on the model for end-stage liver disease score

Renal function has a significant impact on early mortality in patients with cirrhosis. However, creatinine and creatinine-based equations are inaccurate markers of renal function in cirrhosis. The aim of this study was to reassess correlations between creatinine-based equations and measured glomerular filtration rate (GFR) and to investigate the impact of inaccuracies on the Model for End-Stage Liver Disease (MELD) score. GFR was measured using iohexol clearance and calculated with creatinine-based equations in 157 patients with cirrhosis during pretransplant evaluation. We compared the accuracy of creatinine to that of true GFR in a prognostic score also including bilirubin and the international normalized ratio. In patients with creatinine below 1 mg/dL, true GFR ranged from 34-163 mL/minute/1.73 m(2). Cockcroft and Modification of Diet in Renal Disease (MDRD) significantly overestimated true GFR. On multivariate analysis, younger age and ascites were significantly correlated with the overestimation of true GFR by 20% or more. Body mass index was an independent risk factor of overestimation of GFR with Cockcroft but not with MDRD. The accuracy of a prognostic score combining bilirubin, international normalized ratio, and true GFR was superior to that of MELD, whether creatinine was rounded to 1 mg/dL when lower than 1 mg/dL or not (c-statistic of 0.8 versus 0.75 and 0.73, respectively). Creatinine-based formulas overestimate true GFR, especially in patients younger than 50 years or with ascites. In patients with serum creatinine below 1 mg/dL, the spectrum of true GFR is large. True GFR seems to have a better prognostic value than creatinine and creatinine-based equations. Specific equations are needed in patients with cirrhosis to improve prognostic scores.

Gender disparity in liver transplant waiting-list mortality: the importance of kidney function

Previous studies of men and women on the liver transplantation (LT) waiting list, without taking transplantation rates into account, have suggested a higher risk of mortality for women on the waiting list. The objective of this study was to compare men and women with respect to dying within 3 years of registration on the LT waiting list and to take into account both the immediate mortality risks and the transplantation rates. The analysis was based on Organ Procurement and Transplantation Network data for patients with end-stage liver disease (ESLD) on the waiting list who were registered between February 2002 and August 2009. Competing risk survival analysis was performed to assess the gender disparity in waiting-list mortality; 42,322 patients and 610,762 person-months of waiting-list experience were included in the analysis. The risk of dying within 3 years of listing was 19% and 17% in women and men, respectively (P < 0.0001). Among patients with kidney disease and especially those not on dialysis with an estimated glomerular filtration rate (eGFR) ≥15 and <30 mL/minute/1.73 m(2), women had a substantially higher risk of dying on the waiting list within 3 years of registration versus men (26% versus 20%, P = 0.001). This disparity was related to lower transplantation rates in women (transplantation rate ratio = 0.68, P < 0.0001). Controlling for eGFR and other variables related to mortality risk, we found that the overall female-male disparity disappeared. In conclusion, among patients with ESLD and kidney dysfunction who are not on dialysis, there is a substantial gender disparity in LT waiting-list mortality. Our analysis suggests as an explanation the fact that women have lower transplantation rates than men in this group. The lower transplantation rates can be explained in part by the fact that Model for End-Stage Liver Disease scores tend to be lower for women versus men because they are based on serum creatinine rather than the glomerular filtration rate.

Comparison of cystatin C and creatinine-based glomerular filtration rate formulas with 51Cr-EDTA clearance in patients with cirrhosis

BACKGROUND AND OBJECTIVES

Renal function is an important predictor of survival in cirrhosis and liver transplantation. GFR estimates using serum cystatin C (CysC) are proposed as better predictors of renal function than ones on the basis of serum creatinine (Cr). Our aims were: (1) evaluate correlations between serum CysC and different methods of creatinine measurements; (2) compare CysC and Cr GFR formulas with (51)Cr-EDTA; and (3) evaluate liver-related parameters potentially influencing GFR.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

254 blood samples in 65 patients with cirrhosis correlating CysC with four Cr methods were used; another 74 patients comparing (51)Cr-EDTA GFR to Modification of Diet in Renal Disease and Larsson and Hoek formulas for CysC were also included. Agreement was assessed using Bland-Altman plots and concordance correlation coefficients. Multivariate linear regression analysis was used for GFR predictors.

RESULTS

Serum CysC correlated modestly with O'Leary modified Jaffe, compensated kinetic Jaffe, enzymatic creatinine, and standard kinetic Jaffe 0.72/0.71/0.72/0.72 (all P < 0.001). Bland-Altman agreement with (51)Cr-EDTA GFR was poor; the best agreement was Modification of Diet in Renal Disease (concordance 0.61; 95% CI, 0.47 to 0.71); the worst agreement was the Hoek formula (concordance 0.46; 95% CI, 0.27 to 0.61). A new GFR formula including the Child-Pugh score improved the accuracy of Cr GFR formulas compared with (51)Cr-EDTA GFR.

CONCLUSIONS

Estimated GFR in cirrhosis is not better with CysC formulas compared with creatinine ones: specific formulas may be necessary.

Estimation of glomerular filtration rate in liver-transplanted children: comparison of simplified procedures using 51Cr-EDTA and endogenous markers with Sapirstein's method as a reference standard

This study evaluated simple procedures for GFR determination in 48 liver-transplanted children. After injection of (51)Cr-EDTA, blood samples were obtained up to four h, and activity retention in the body was measured for 60 min with scintillation probes. As a reference, GFR was calculated according to Sapirstein. Simplified calculations were performed according to Brochner-Mortensen, Russel, Devaux and Oberhausen. Additionally, GFR was determined using plasma creatinine and cystatin C according to Schwartz and Filler, respectively. The reference revealed mildly reduced GFR (62 +/- 20 mL/min/1.73 m(2)). Russel's method provided the highest degree of correlation (r(2) = 0.95), the smallest bias in GFR determination (-2%), and only one false exclusion plus one false diagnosis of chronic kidney disease. Oberhausen's method with blood sampling at one h post-injection performed slightly worse (r(2) = 0.67, bias: 3%). All other methods resulted in significantly different GFR estimates compared to the reference. Nevertheless, notably, the second narrowest 95% limits of agreement (-31% to 45%) was observed using cystatin C. In conclusion, this data implies to prefer Russel's method as a simplified procedure, and if patients cannot be available long enough (four h) for measurements, Oberhausen's method instead. If radiotracer methods are not available at all or for screening GFR, cystatin C appears to be the procedure of choice.

Transarterial chemoembolization in patients with hepatocellular carcinoma and renal insufficiency

BACKGROUND

Renal dysfunction is often present in patients with cirrhosis and hepatocellular carcinoma (HCC). Acute renal failure (ARF) may occur after transarterial chemoembolization (TACE) owing to radiocontrast agent. This study investigated the incidence and risk factors of ARF and prognostic predictors in HCC patients with preexisting renal insufficiency undergoing TACE.

METHODS

A total of 566 HCC patients undergoing TACE were enrolled. Renal insufficiency was defined as an estimated glomerular filtration rate less than 60 mL/min/1.73 m.

RESULTS

In a mean follow-up duration of 18+/-16 months, 231 (40.8%) patients undergoing TACE died. Renal insufficiency that was present in 134 (23.7%) patients at baseline, independently predicted a poor prognosis in the Cox proportional hazards model [risk ratio (RR): 1.47, P=0.012]. Of them, 13 (10%) and 6 (5%) patients had transient and prolonged ARF after TACE, respectively. Post-TACE gastrointestinal bleeding [odds ratio (OR): 16.54, P=0.001] and higher Cancer of the Liver Italian Program (CLIP) scores (> or =2; OR: 4.22, P=0.02) were independent risk factors for ARF in the multivariate logistic regression analysis. In the Cox model, prolonged ARF (RR: 3.28, P<0.001) and higher CLIP scores (> or =2; RR: 2.13, P<0.001) were independent poor prognostic predictors for HCC patients with renal insufficiency receiving TACE.

CONCLUSIONS

Gastrointestinal bleeding and higher CLIP scores are associated with the development of ARF in patients with HCC and renal insufficiency undergoing TACE. Higher CLIP scores and renal insufficiency, either preexisting before TACE or as a complication of TACE, are poor prognostic predictors in HCC patients receiving TACE.

Comparative performance of the CKD Epidemiology Collaboration (CKD-EPI) and the Modification of Diet in Renal Disease (MDRD) Study equations for estimating GFR levels above 60 mL/min/1.73 m2

BACKGROUND

The Modification of Diet in Renal Disease (MDRD) Study equation underestimates measured glomerular filtration rate (GFR) at levels>60 mL/min/1.73 m2, with variable accuracy among subgroups; consequently, estimated GFR (eGFR)>or=60 mL/min/1.73 m2 is not reported by clinical laboratories. Here, performance of a more accurate GFR-estimating equation, the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation, is reported by level of GFR and clinical characteristics.

STUDY DESIGN

Test of diagnostic accuracy.

SETTING & PARTICIPANTS

Pooled data set of 3,896 people from 16 studies with measured GFR (not used for the development of either equation). Subgroups were defined by eGFR, age, sex, race, diabetes, prior solid-organ transplant, and body mass index.

INDEX TESTS

eGFR from the CKD-EPI and MDRD Study equations and standardized serum creatinine.

REFERENCE TEST

Measured GFR using urinary or plasma clearance of exogenous filtration markers.

RESULTS

Mean measured GFR was 68+/-36 (SD) mL/min/1.73 m2. For eGFR<30 mL/min/1.73 m2, both equations have similar bias (median difference compared with measured GFR). For eGFR of 30-59 mL/min/1.73 m2, bias was decreased from 4.9 to 2.1 mL/min/1.73 m2 (57% improvement). For eGFR of 60-89 mL/min/1.73 m2, bias was decreased from 11.9 to 4.2 mL/min/1.73 m2 (61% improvement). For eGFR of 90-119 mL/min/1.73 m2, bias was decreased from 10.0 to 1.9 mL/min/1.73 m2 (75% improvement). Similar or improved performance was noted for most subgroups with eGFR<90 mL/min/1.73 m2, other than body mass index<20 kg/m2, with greater variation noted for some subgroups with eGFR>or=90 mL/min/1.73 m2.

LIMITATIONS

Limited number of elderly people and racial and ethnic minorities with measured GFR.

CONCLUSIONS

The CKD-EPI equation is more accurate than the MDRD Study equation overall and across most subgroups. In contrast to the MDRD Study equation, eGFR>or=60 mL/min/1.73 m2 can be reported using the CKD-EPI equation.

What is the best alternative to inulin clearance to estimate GFR in patients with decompensated alcoholic cirrhosis?

BACKGROUND

Accurate evaluation of the glomerular filtration rate (GFR) in patients awaiting liver transplantation is important because they have a greater risk of impaired renal function. A major percentage of these patients have alcoholic cirrhosis, and the accuracy of bedside used GFR estimates have not been specifically evaluated in this group. The aim of this study was to evaluate the validity of the simplified Modification of Diet in Renal Diseases (MDRD) and Cockcroft and Gault (CG) formulas in patients with decompensated alcoholic cirrhosis in comparison to inulin clearance as the reference method.

METHODS

GFR estimated by the simplified MDRD and CG formulas were retrospectively compared to the true GFR measured by inulin clearance in a single-centre cohort of 148 patients with decompensated alcoholic cirrhosis.

RESULTS

Mean ± standard deviation of age, body mass index, inulin clearance and MDRD and CG estimates were 54.4 ± 6.9 years, 26.5 ± 4.7 kg/m(2), 76.9 ± 28.0 mL/min per 1.73 m(2), 99.4 ± 34.0 mL/min per 1.73 m(2) and 98.7 ± 32.0 mL/min per 1.73 m(2), respectively; 70% of the patients had a GFR, measured by inulin clearance, below 90 mL/min per 1.73 m(2). The difference between estimated GFR and true GFR were 23 ± 23 mL/min per 1.73 m(2) for MDRD and 22 ± 20 mL/min per 1.73 m(2) for Cockcroft and Gault.

CONCLUSIONS

The simplified MDRD and CG formulas largely overestimated GFR in patients with decompensated alcoholic cirrhosis. Results of such bedside formulas should be interpreted with caution in these patients.

The evaluation of renal function and disease in patients with cirrhosis

The MELD score has shown that, besides markers of liver function, serum creatinine has a strong prognostic value in cirrhosis. However, even though creatinine has a good prognostic value, it is an inaccurate marker of renal function in cirrhosis. Creatinine and creatinine-based equations tend to overestimate glomerular filtration rate (GFR), and creatinine clearance from timed urine collection also overestimates GFR. Hence, clearance of exogenous markers such as iohexol remains the only reliable method for assessing precisely GFR in cirrhosis. Whereas these investigations are limited by their costs and complexity, and they can hardly be repeated at short intervals, serum cystatin C could be an alternative, although it needs further validation. Accurate markers and/or specific equations are therefore still needed to assess GFR in cirrhotic patients. Pre-renal failure and hepatorenal syndrome (HRS) are the main causes of acute renal failure in cirrhosis. Both result from decreased renal blood flow and both can result in acute tubular necrosis. HRS is not always fully reversible with liver transplantation possibly due to underlying chronic kidney damage. A number of cirrhotic patients with acute renal failure may also have chronic kidney damage ("acute-on-chronic renal failure"); furthermore, cirrhotic patients frequently have co-morbidities such as diabetes that may result in chronic impairment in renal function. Since conventional urinary markers are biased in cirrhosis, a biopsy is the only way to document and quantify renal lesions; moreover, transvenous route should be preferred to percutaneous route. In candidates for transplantation, attention should therefore be focused on vascular lesions which may represent a risk factor for nephrotoxicities induced by calcineurin-inhibitors.

Serum sodium, renal function, and survival of patients with end-stage liver disease

BACKGROUND & AIMS

Serum creatinine, a component of the model for end-stage liver disease (MELD), is an important prognostic indicator in patients with end-stage liver disease (ESLD). In addition, serum sodium has recently been recognized as an important predictor of mortality in patients with ESLD. We investigate the role of serum creatinine and sodium, and glomerular filtration rate (GFR) as determinants of survival in patients with ESLD.

METHODS

A prospective database was utilized to identify all adults listed for primary liver transplantation (LTx) at the Mayo Clinic, Rochester, between 1990 and 1999. GFR was measured by iothalamate clearance.

RESULTS

Among 837 patients listed for LTx, 660 had complete data including measured GFR. There was a significant association between GFR and survival after adjustment for MELD, with a linear rise in the risk of death as GFR decreased between 60 and 20ml/min/1.73m(2). Multivariable models showed that GFR is superior to creatinine in predicting mortality - a model consisting of total bilirubin (hazard ratio (HR)=2.17, p<0.01), INR (HR=3.26, p<0.01) and GFR (HR=0.42, p<0.01) was superior to MELD (chi-square 65.6 vs. 59.4, c-statistic 0.792 vs. 0.780). Serum sodium did not contribute to survival prediction when accurately measured GFR data were available.

CONCLUSIONS

Serum concentrations of creatinine and sodium in patients with end-stage liver disease reflect a reduction in renal function, the underlying event that decreases survival.

Pretransplant predictors of recovery of renal function after liver transplantation

The Model for End-Stage Liver Disease system has given priority on the liver transplant waiting list to candidates with renal failure. This study determined the predictors of spontaneous recovery of renal function after transplantation in 1041 liver transplant recipients on renal replacement therapy (RRT) at the time of transplant (from February 2002 to January 2007). Data from these patients were obtained from the US Organ Procurement and Transplantation Network and US Renal Data System databases. Univariate and multivariate survival models were constructed along with multivariate logistic regression models to find independent predictors of spontaneous renal recovery. Seven hundred seven recipients (67.9%) had spontaneous recovery of renal function after liver transplantation. Those recovering spontaneously had a significantly shorter course of RRT in the pretransplant time period (15.6 versus 36.6 days, P < 0.001). Recovery of renal function was observed in 70.8% and 11.5% of recipients on RRT for less than 30 days and more than 90 days, respectively. Other statistically significant pretransplant variables independently associated with recovery of renal function included recipient age, recipient pretransplant diabetes, and donor age. In conclusion, the duration of pretransplant RRT is highly predictive of spontaneous renal recovery post-transplant. Liver transplant candidates requiring less than 30 days of pretransplant RRT are likely to spontaneously recover renal function after liver transplantation, whereas those on RRT for more than 90 days are not.

Predicting renal failure after liver transplantation from measured glomerular filtration rate: review of up to 15 years of follow-up

BACKGROUND

The immunosuppressive medications that have contributed greatly to the success of liver transplantation are also associated with posttransplant renal dysfunction. We reviewed measured glomerular filtration rate (GFR) data from patients who underwent transplantation more than 10 years ago to assess whether results from specific time points can predict renal failure.

METHODS

The GFR data were obtained at initial evaluation (IE), at month 3, and at years 1, 2, 5, 10, and 15. Two groupings were compared, one based on GFR at IE and the other at month 3. Patients were further stratified into three GFR (mL/min/1.73 m2) groups: G1, GFR more than 80; G2, GFR 60 to 80; and G3, GFR less than 60.

RESULTS

A total of 592 liver transplant recipients met the inclusion criteria; 114 had paired GFR data from IE to year 15. Analysis of paired and censored data based on IE GFR showed that 62.2% of G3 patients developed renal failure by year 5; another 6.7% did so by year 10 (P=0.027). The month 3 GFR data showed that 56.3% of G3 patients developed renal failure by year 5; another 15.6% did so by year 10. Surprisingly, 37.0% of G2 patients experienced renal failure by year 5; another 11.1% did so by year 10 (P=0.0024).

CONCLUSIONS

The month 3 data indicate a slow but steady decline in GFR over years. The lower the initial GFR is after transplant, the sooner renal failure develops. Patients with GFR less than 60 mL/min per 1.73 m2 at month 3 have a higher risk of renal failure; however, those who avoid renal failure seem to maintain renal function long term.

Renal failure in patients with hepatocellular carcinoma and ascites undergoing transarterial chemoembolization

BACKGROUND

Ascites is often present in patients with hepatocellular carcinoma (HCC) with cirrhosis. Advanced cirrhosis may predispose to renal dysfunction. Acute renal failure (ARF) may occur after transarterial chemoembolization (TACE) for HCC because of radiocontrast agents. This study aimed to investigate the incidence and risk factors of ARF and prognostic predictors in HCC patients with ascites undergoing TACE.

METHODS

A total of 591 HCC patients receiving TACE were enrolled.

RESULTS

In a mean follow-up duration of 19+/-17 months, 239 (40.4%) patients undergoing TACE died. Ascites, which was present in 91 (15.4%) patients at entry, independently predicted a poor prognosis in the Cox proportional hazard model [risk ratio (RR): 1.71, P=0.002]. Of these, 11 (12.6%) of 87 patients with complete follow-up developed ARF after TACE. Serum albumin level <3.3 g/dl (odds ratio: 7.3, P=0.009) was the only independent risk factor associated with ARF in the logistic regression analysis. ARF (RR: 2.17, P=0.036), alpha-fetoprotein >400 ng/ml (RR: 1.84, P=0.04), multiple tumours (RR: 2.11, P=0.013), tumour size > or = 5 cm (RR: 2.32, P=0.006) and serum sodium level <139 mmol/L (RR: 2.4, P=0.005) were independent poor prognostic predictors for HCC patients with ascites receiving TACE.

CONCLUSIONS

Pre-existing ascites is associated with increased mortality in HCC patients receiving TACE. In HCC patients with ascites, hypoalbuminaemia is associated with the occurrence of post-TACE ARF. Post-TACE ARF is a poor prognostic predictor in this subset of HCC patients.

Evaluating cimetidine for GFR estimation in liver transplant recipients

Background. Serum creatinine (Scr)-based equations lack accuracy in predicting glomerular filtration rate (GFR) in patients with liver disease. Cimetidine has been shown to improve the performance of Scr-based GFR formulae. Methods. We evaluated the use of cimetidine on the performance of GFR-estimating equations in 39 liver transplant recipients. The patients received oral cimetidine (800 mg tid) during a 24-h urine collection. The next day, the patients underwent radionucleotide GFR (rGFR) determination and Scr was measured for creatinine clearance (CrCl) and GFR estimation using the Cockcroft-Gault, Nankivell and modified diet in renal disease (MDRD) equations. Data were analysed using the Pearson correlation statistic and Bland-Altman plots. Results. The mean rGFR was 65 +/- 26.4 mL/min. The use of cimetidine increased the bias between rGFR and the Nankivell and MDRD equations. The combined root mean square error for the CrCl, Cockcroft-Gault, Nankivell and MDRD equations without cimetidine were 20.2, 15.6, 17.0 and 15.5 and cimetidine-aided were 28.2, 23.2, 23.7 and 24.3, respectively. Conclusions. All the tested equations without using cimetidine predicted GFR with modest accuracy. The addition of cimetidine decreased the precision and increased the bias of all the GFR-estimating equations. In the absence of accurate GFR-estimating equations, rGFR should be used to monitor kidney function in liver transplant recipients.

Outcomes after liver transplantation: chronic kidney disease

1. Chronic kidney disease is a common complication after liver transplantation and has a major impact on graft and patient survival. 2. Pretransplant renal dysfunction is the most important determinant of posttransplant chronic kidney disease; other factors include the presence of diabetes/hypertension, acute kidney injury pre-transplant and post-transplant, and the use of calcineurin inhibitor-based immunosuppression. 3. The most common cause of end-stage renal disease post-orthotopic liver transplantation is calcineurin inhibitor toxicity, and this emphasizes the need for calcineurin inhibitor minimization protocols post-transplant. 4. The presence of chronic kidney disease post-orthotopic liver transplantation not only is important with respect to the need for renal replacement therapy and kidney transplantation but also increases cardiovascular risk dramatically. 5. The Model for End-Stage Liver Disease score is partly driven by creatinine, and it is not uncommon to have an elevated creatinine level in those who have a high Model for End-Stage Liver Disease score and are close to having an organ allocated. Thus, evaluating patients with advanced liver disease and pretransplant acute kidney injury is challenging. It is important to identify pre-liver transplant patients at high risk for early evolution of chronic kidney disease post-transplant in order to appropriately select patients for combined liver/kidney transplantation.

Development and validation of GFR-estimating equations using diabetes, transplant and weight

BACKGROUND

We have reported a new equation (CKD-EPI equation) that reduces bias and improves accuracy for GFR estimation compared to the MDRD study equation while using the same four basic predictor variables: creatinine, age, sex and race. Here, we describe the development and validation of this equation as well as other equations that incorporate diabetes, transplant and weight as additional predictor variables.

METHODS

Linear regression was used to relate log-measured GFR (mGFR) to sex, race, diabetes, transplant, weight, various transformations of creatinine and age with and without interactions. Equations were developed in a pooled database of 10 studies [2/3 (N = 5504) for development and 1/3 (N = 2750) for internal validation], and final model selection occurred in 16 additional studies [external validation (N = 3896)].

RESULTS

The mean mGFR was 68, 67 and 68 ml/min/ 1.73 m(2) in the development, internal validation and external validation datasets, respectively. In external validation, an equation that included a linear age term and spline terms in creatinine to account for a reduction in the magnitude of the slope at low serum creatinine values exhibited the best performance (bias = 2.5, RMSE = 0.250) among models using the four basic predictor variables. Addition of terms for diabetes and transplant did not improve performance. Equations with weight showed a small improvement in the subgroup with BMI <20 kg/m(2).

CONCLUSIONS

The CKD-EPI equation, based on creatinine, age, sex and race, has been validated and is more accurate than the MDRD study equation. The addition of weight, diabetes and transplant does not significantly improve equation performance.

Renal outcomes after liver transplantation in the model for end-stage liver disease era

The proportion of patients undergoing liver transplantation (LT) with renal insufficiency has significantly increased in the Model for End-Stage Liver Disease (MELD) era. This study was designed to determine the incidence and predictors of post-LT chronic renal failure (CRF) and its effect on patient survival in the MELD era. Outcomes of 221 adult LT recipients who had LT between February 2002 and February 2007 were reviewed retrospectively. Patients who were listed as status 1, were granted a MELD exception, or had living-donor, multiorgan LT were excluded. Renal insufficiency at LT was defined as none to mild [estimated glomerular filtration rate (GFR) >or= 60 mL/minute], moderate (30-59 mL/minute), or severe (<30 mL/minute). Post-LT CRF was defined as an estimated GFR < 30 mL/minute persisting for 3 months, initiation of renal replacement therapy, or listing for renal transplantation. The median age was 54 years, 66% were male, 89% were Caucasian, and 43% had hepatitis C. At LT, the median MELD score was 20, and 6.3% were on renal replacement therapy. After a median follow-up of 2.6 years (range, 0.01-5.99), 31 patients developed CRF with a 5-year cumulative incidence of 22%. GFR at LT was the only independent predictor of post-LT CRF (hazard ratio = 1.33, P < 0.001). The overall post-LT patient survival was 74% at 5 years. Patients with MELD >or= 20 at LT had a higher cumulative incidence of post-LT CRF in comparison with patients with MELD < 20 (P = 0.03). A decrease in post-LT GFR over time was the only independent predictor of survival. In conclusion, post-LT CRF is common in the MELD era with a 5-year cumulative incidence of 22%. Low GFR at LT was predictive of post-LT CRF, and a decrease in post-LT GFR over time was associated with decreased post-LT survival. Further studies of modifiable preoperative, perioperative, and postoperative factors influencing renal function are needed to improve outcomes following LT.

Long-term management of the liver transplant patient: recommendations for the primary care doctor

No official document has been published for primary care physicians regarding the management of liver transplant patients. With no official source of reference, primary care physicians often question their care of these patients. The following guidelines have been approved by the American Society of Transplantation and represent the position of the association. The data presented are based on formal review and analysis of published literature in the field and the clinical experience of the authors. These guidelines address drug interactions and side effects of immunosuppressive agents, allograft dysfunction, renal dysfunction, metabolic disorders, preventive medicine, malignancies, disability and productivity in the workforce, issues specific to pregnancy and sexual function, and pediatric patient concerns. These guidelines are intended to provide a bridge between transplant centers and primary care physicians in the long-term management of the liver transplant patient.

Long-term renal function in liver transplant recipients and impact of immunosuppressive regimens (calcineurin inhibitors alone or in combination with mycophenolate mofetil): the TRY study

The prevalence of renal insufficiency before and at 1, 12, and 60 months after liver transplantation (LTx; primary endpoint) and the changes in the glomerular filtration rate (GFR) at same time points according to the immunosuppressive regimen (coprimary endpoint) were investigated. The primary outcome was determined for the entire cohort, whereas the coprimary endpoint was determined only for 2 groups of patients: those who started and remained on a calcineurin inhibitor (CNI) alone, that is, the CNI-alone group (n = 624), and those who started and remained on a CNI in combination with mycophenolate mofetil (MMF), that is, the MMF group (n = 117). GFR was <60 mL/minute/1.73 kg/m(2) in 11%, 48%, 51% and 58% of the patients at baseline and at 1, 12, and 60 months, respectively. The decrease in GFR was significantly lower in the MMF group compared to the CNI-alone group at 12 and 60 months (-16% versus -30% and -15% versus -33%, respectively), whereas the GFR decrease at 1 month was not different between the 2 groups. There were no significant differences between the 2 groups in CNI doses or blood levels at 12 and 60 months. In conclusion, there was a worsening of renal failure in 83% of patients post-LTx; 58% and 5% had GFRs of <60 and <30 mL/minute/1.73 kg/m(2), respectively, at 5 years after LTx. The reduction of the GFR was significantly less marked in the MMF group compared to the CNI-alone group, and this could be related to less important CNI exposure early after LTx. It seems likely that early intervention for CNI reduction is best for reducing the use of CNIs in the long term.

Cystatin C and cardiovascular risk

BACKGROUND

Patients with chronic kidney disease (CKD) are at high risk for developing cardiovascular disease (CVD) and cardiovascular events. Cystatin C, a protease inhibitor synthesized in all nucleated cells, has been proposed as a replacement for serum creatinine for the assessment of renal function, particularly to detect small reductions in glomerular filtration rate.

CONTENT

This report presents a review of the role of cystatin C as a predictor of cardiovascular risk.

SUMMARY

Patients with higher circulating cystatin C concentrations appear to have an increased cardiovascular risk profile, i.e., they are older and have a higher prevalence of systemic hypertension, dyslipidemia, documented CVD, increased body mass index, and increased concentrations of C-reactive protein. Prospective studies have shown, in various clinical scenarios, that patients with increased cystatin C are at a higher risk of developing both CVD and CKD. Importantly, cystatin C appears to be a useful marker for identifying individuals at a higher risk for cardiovascular events among patients belonging to a relatively low-risk category as assessed by both creatinine and estimated glomerular filtration rate values. Of interest, elastolytic proteases and their inhibitors, in particular cystatin C, have been shown to be directly involved in the atherosclerotic process. Increased concentrations of cystatin C appear to be indicative of preclinical kidney disease associated with adverse outcomes. Clinical studies involving direct glomerular filtration rate measurements are required to ascertain both the true role of this promising marker in renal disease and whether atherogenic factors like inflammation can account for increases in cystatin C concentrations, thus explaining its predictive value in CVD.

Renal impairment after liver transplantation - a pilot trial of calcineurin inhibitor-free vs. calcineurin inhibitor sparing immunosuppression in patients with mildly impaired renal function after liver transplantation

Objectives

Chronic kidney disease is frequent in patients after orthotopic liver transplantation (OLT) and has impact on survival. Patients receiving calcineurin inhibitors (CNI) are at increased risk to develop impaired renal function. Early CNI reduction and concomitant use of mycophenolat mofetil (MMF) has been shown to improve renal function.

Methods

The aim of this trial was to compare dose-reduced CNI/MMF versus CNI-free MMF/prednisone-based treatment in stable patients after OLT with respect to glomerular filtration rate (GFR). 21 patients [GFR 44.9 ± 9.9 mL/min/1.73 m² measured by 99m-Tc-DTPA-clearance, serum creatinine (SCr) 1.5 ± 0.42 mg/dL] were randomized either to exchange CNI for 10 mg prednisone (group 1; n = 8) or to receive CNI at 25% of the initial dose (group 2; n = 13) each in combination with 1000 mg MMF b.i.d.

Results

At month 12 mean SCr (-0.3 ± 0.4 mg/dL, p = 0.031) and GFR improved (8.6 ± 13.1 mL/min/1.73 m², p = 0.015) in group 2 but remained unchanged in group 1. Main side effects were gastroinstestinal symptoms (14.3%) and infections (4.8%). Two biopsy proven, steroid-responsive rejections occurred. In group 1 mean diastolic blood pressure (BP) increased by 11 ± 22 mmHg (p = 0.03).

Conclusions

Reduced dose CNI in combination with MMF but not CNI-free-immunosuppression leads to improvement of GFR in patients with moderately elevated SCr levels after OLT. Addition of steroids resulted in increased diastolic blood pressure presumably counterbalancing the benefits of CNI withdrawal on renal function.

Comparison of drug dosing recommendations based on measured GFR and kidney function estimating equations

BACKGROUND

Kidney disease alters the pharmacokinetic disposition of many medications, requiring dosage adjustment to maintain therapeutic serum concentrations. The Cockcroft-Gault (CG) equation is used for pharmacokinetic studies and drug dosage adjustments, but the Modification of Diet in Renal Disease (MDRD) Study equation is more accurate and more often reported by clinical laboratories than the CG equation.

STUDY DESIGN

Diagnostic test study.

SETTINGS & PARTICIPANTS

Pooled data set for 5,504 participants from 6 research studies and 4 clinical populations with measured glomerular filtration rate (GFR).

INDEX TEST

Estimated kidney function using the MDRD Study and CG equations incorporating actual (CG) or ideal body weight (CG(IBW)) and standardized serum creatinine concentrations.

REFERENCE TEST

Measured GFR assessed by using iodine-125-iothalamate urinary clearance.

OUTCOME

Concordance of assigned kidney function categories designated by the Food and Drug Administration (FDA) Guidance for Industry for pharmacokinetic studies and recommended dosages of 15 medications cleared by the kidneys.

RESULTS

Concordance of kidney function estimates with measured GFR for FDA-assigned kidney function categories was 78% for the MDRD Study equation compared with 73% for the CG equation (P < 0.001) and 66% for the CG(IBW) equation (P < 0.001). Concordance between the MDRD Study equation and CG and CG(IBW) equations was 78% and 75%, respectively (P < 0.001). Concordance of kidney function estimates with measured GFR for recommended drug dosages was 88% for MDRD Study equation compared with 85% for the CG equation (P < 0.001) and 82% for the CG(IBW) equation (P < 0.001), with lower concordance when dosing recommendations for drugs included narrow GFR ranges. Concordance rates between the CG and CG(IBW) equations and MDRD Study equation were 89% and 88%, respectively (P < 0.05).

LIMITATIONS

Results based on simulation rather than pharmacokinetic studies. Outcome was drug dosage recommendations, rather than observed drug efficacy and safety.

CONCLUSIONS

The MDRD Study equation can also be used for pharmacokinetic studies and drug dosage adjustments. As more accurate GFR-estimating equations are developed, they should be used for these purposes.

Renal failure in patients with cirrhosis

Renal failure in cirrhosis poses unique diagnostic and therapeutic challenges. Laboratory values and predictive equations grossly overestimate renal function in patients with cirrhosis. Development of renal failure connotes a worse prognosis; mortality is especially high with hepatorenal syndrome. Classification of the causes of renal failure in patients with cirrhosis is provided with more extensive discussion of selected causes. Finally, a suggested diagnostic approach to renal failure in cirrhosis is given.

Simultaneous liver-kidney transplantation in the MELD era

Impaired kidney function is common in liver transplant candidates and portends heightened risk for both postoperative chronic kidney disease and mortality. The weighting of serum creatinine in the Model of End-stage Liver Disease classification for liver allocation has been accompanied by a proliferation of simultaneous liver-kidney transplants in recent years. In the absence of standardized criteria for allocating kidneys in this setting, there is a wide variation in combined organ transplants across transplant centers. This review discusses the issues surrounding simultaneous liver-kidney transplantation and proposes a strategy for selecting patients to receive both organs.

A new equation to estimate glomerular filtration rate

BACKGROUND

Equations to estimate glomerular filtration rate (GFR) are routinely used to assess kidney function. Current equations have limited precision and systematically underestimate measured GFR at higher values.

OBJECTIVE

To develop a new estimating equation for GFR: the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation.

DESIGN

Cross-sectional analysis with separate pooled data sets for equation development and validation and a representative sample of the U.S. population for prevalence estimates.

SETTING

Research studies and clinical populations ("studies") with measured GFR and NHANES (National Health and Nutrition Examination Survey), 1999 to 2006.

PARTICIPANTS

8254 participants in 10 studies (equation development data set) and 3896 participants in 16 studies (validation data set). Prevalence estimates were based on 16,032 participants in NHANES.

MEASUREMENTS

GFR, measured as the clearance of exogenous filtration markers (iothalamate in the development data set; iothalamate and other markers in the validation data set), and linear regression to estimate the logarithm of measured GFR from standardized creatinine levels, sex, race, and age.

RESULTS

In the validation data set, the CKD-EPI equation performed better than the Modification of Diet in Renal Disease Study equation, especially at higher GFR (P < 0.001 for all subsequent comparisons), with less bias (median difference between measured and estimated GFR, 2.5 vs. 5.5 mL/min per 1.73 m(2)), improved precision (interquartile range [IQR] of the differences, 16.6 vs. 18.3 mL/min per 1.73 m(2)), and greater accuracy (percentage of estimated GFR within 30% of measured GFR, 84.1% vs. 80.6%). In NHANES, the median estimated GFR was 94.5 mL/min per 1.73 m(2) (IQR, 79.7 to 108.1) vs. 85.0 (IQR, 72.9 to 98.5) mL/min per 1.73 m(2), and the prevalence of chronic kidney disease was 11.5% (95% CI, 10.6% to 12.4%) versus 13.1% (CI, 12.1% to 14.0%).

LIMITATION

The sample contained a limited number of elderly people and racial and ethnic minorities with measured GFR.

CONCLUSION

The CKD-EPI creatinine equation is more accurate than the Modification of Diet in Renal Disease Study equation and could replace it for routine clinical use.

PRIMARY FUNDING SOURCE

National Institute of Diabetes and Digestive and Kidney Diseases.

Comparison of drug dosing recommendations based on measured GFR and kidney function estimating equations

BACKGROUND

Kidney disease alters the pharmacokinetic disposition of many medications, requiring dosage adjustment to maintain therapeutic serum concentrations. The Cockcroft-Gault (CG) equation is used for pharmacokinetic studies and drug dosage adjustments, but the Modification of Diet in Renal Disease (MDRD) Study equation is more accurate and more often reported by clinical laboratories than the CG equation.

STUDY DESIGN

Diagnostic test study.

SETTINGS & PARTICIPANTS

Pooled data set for 5,504 participants from 6 research studies and 4 clinical populations with measured glomerular filtration rate (GFR).

INDEX TEST

Estimated kidney function using the MDRD Study and CG equations incorporating actual (CG) or ideal body weight (CG(IBW)) and standardized serum creatinine concentrations.

REFERENCE TEST

Measured GFR assessed by using iodine-125-iothalamate urinary clearance.

OUTCOME

Concordance of assigned kidney function categories designated by the Food and Drug Administration (FDA) Guidance for Industry for pharmacokinetic studies and recommended dosages of 15 medications cleared by the kidneys.

RESULTS

Concordance of kidney function estimates with measured GFR for FDA-assigned kidney function categories was 78% for the MDRD Study equation compared with 73% for the CG equation (P < 0.001) and 66% for the CG(IBW) equation (P < 0.001). Concordance between the MDRD Study equation and CG and CG(IBW) equations was 78% and 75%, respectively (P < 0.001). Concordance of kidney function estimates with measured GFR for recommended drug dosages was 88% for MDRD Study equation compared with 85% for the CG equation (P < 0.001) and 82% for the CG(IBW) equation (P < 0.001), with lower concordance when dosing recommendations for drugs included narrow GFR ranges. Concordance rates between the CG and CG(IBW) equations and MDRD Study equation were 89% and 88%, respectively (P < 0.05).

LIMITATIONS

Results based on simulation rather than pharmacokinetic studies. Outcome was drug dosage recommendations, rather than observed drug efficacy and safety.

CONCLUSIONS

The MDRD Study equation can also be used for pharmacokinetic studies and drug dosage adjustments. As more accurate GFR-estimating equations are developed, they should be used for these purposes.

The impact of MELD allocation on simultaneous liver-kidney transplantation

Model for End-Stage Liver Disease (MELD) allocation has improved the process for ranking patients on the liver transplant list. One unintended consequence has been an increase in the number of simultaneous liver-kidney (SLK) transplants. Some have argued that the system unfairly advantages patients with kidney disease and that some kidneys are being prematurely placed in SLK transplantation. This review summarizes the MELD score, assessment of kidney function in cirrhosis, the impact of kidney function in liver disease, and changes in kidney function status in liver transplant recipients in the MELD era. Finally, recommendations regarding who should receive SLK transplants are reviewed.