Evaluating cimetidine for GFR estimation in liver transplant recipients

Serum Cystatin C as an Indicator of Renal Function and Mortality in Liver Transplant Recipients

BACKGROUND/AIMS

Chronic kidney disease (CKD) is an important comorbidity after liver transplantation (LT); however, reliable tools with which to evaluate these patients are limited. In this work, we examine the extent to which the addition of serum cystatin C improves glomerular filtration rate (GFR) estimation and mortality prediction, in comparison to various GFR-estimating equations.

METHODS

The GFR was measured in LT recipients by iothalamate clearance. Concurrent serum cystatin C was assayed in banked serum samples. Performance of GFR-estimating equations with and without cystatin C, including the modification of diet in renal disease and CKD-epidemiology collaboration formulas was assessed. The proportional hazards regression analysis was performed to determine the association between serum cystatin C and mortality.

RESULTS

A total of 586 iothalamate results were obtained in 401 patients after a mean of 4 years after LT. When compared to measured GFR, the formula with both creatinine and cystatin C, namely, CKD-epidemiology cr-cys, outperformed those with either marker alone. Performance of creatinine-based models was similar to one another. Serum cystatin C, by itself or as a part of an estimated GFR, was a significant predictor of mortality.

CONCLUSIONS

Serum cystatin C has an important role in enhancing accuracy of GFR estimation and predicting mortality in LT recipients.

Accuracy of urine collection methods compared to measured GFR in adults with liver disease

BACKGROUND

Assessment of kidney function is necessary to stage kidney disease, dose medications, and to make decisions about organ allocation. Estimating equations that incorporate serum creatinine (SCr) are not consistently reliable. However, assessment of creatinine clearance (CrCl) using 24-hour urine collection methods is also prone to errors. The purpose of this study was to evaluate the accuracy of measured CrCl determined using shorter urine collection times compared to glomerular filtration rate measured by (125)I-iothalamate clearance ((125)I-CL) in patients with liver disease.

METHODS

Adult patients with chronic liver disease were enrolled. All patients received (125)I-iothalamate and had a catheter placed for urine collection. Blood samples were collected at designated times over 8 hours to determine (125)I-CL. CrCl was determined from a 1-hour and a 4-hour urine collection and compared to (125)I-CL.

RESULTS

Characteristics of the eight patients enrolled included age 52 ± 6 years; SCr 1.2 ± 0.4 mg/dL; and Model for End-stage Liver Disease score of 13 ± 3. All patients were Child-Pugh Class B. Mean estimates of kidney function (mean ± SD, mL/min/1.73 m(2)) by method were 74 ± 38 for (125)I-CL, 79 ± 28 for the 1-hour urine collection, and 72 ± 26 for the 4-hour urine collection. Measured CrCl did not differ significantly from (125)I-CL (P = .641 for 1-hour CrCl versus (125)I-CL, and P = 1.0 for the 4-hour CrCl versus (125)I-CL).

CONCLUSION

When urine collection methods are necessary for an individualized assessment of kidney function, shorter collection times can provide accurate results and would be more feasible for the patient.

Performance of creatinine-based GFR estimating equations in solid-organ transplant recipients

BACKGROUND

Accurate assessment of kidney function is important for the management of solid-organ transplant recipients. In other clinical populations, glomerular filtration rate (GFR) most commonly is estimated using the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) creatinine or the 4-variable MDRD (Modification of Diet in Renal Disease) Study equation. The accuracy of these equations compared with other GFR estimating equations in transplant recipients has not been carefully studied.

STUDY DESIGN

Diagnostic test study.

SETTING & PARTICIPANTS

Solid-organ transplant recipients longer than 6 months posttransplantation from 5 clinical populations (N=3,622, including recipients of kidney [53%], liver [35%], and other or multiple organs [12%]).

INDEX TEST

Estimated GFR (eGFR) using creatinine-based GFR estimating equations identified from a systematic review of the literature. Performance of the CKD-EPI creatinine and the MDRD Study equations was compared with alternative equations.

REFERENCE TEST

Measured GFR (mGFR) from urinary clearance of iothalamate or plasma clearance of iohexol.

MEASUREMENTS

Error (difference between mGFR and eGFR) expressed as P30 (proportion of absolute percent error <30%) and mean absolute error.

RESULTS

We identified 26 GFR estimating equations. Mean mGFR was 55.1±22.7 (SD) mL/min/1.73 m(2). P30 and mean absolute error for the CKD-EPI and the MDRD Study equations were 78.9% (99.6% CI, 76.9%-80.8%) for both and 10.6 (99.6% CI, 10.1-11.1) versus 11.0 (99.6% CI, 10.5-11.5) mL/min/1.73 m(2), respectively; these equations were more accurate than any of the alternative equations (P <0.001 for all pairwise comparisons for both measures). They performed better than or as well as the alternative equations in most subgroups defined by demographic and clinical characteristics, including type of transplanted organ.

LIMITATIONS

Study population included few nonwhites and people with solid-organ transplants other than liver and kidneys.

CONCLUSIONS

The CKD-EPI creatinine and the MDRD Study equations perform better than the alternative creatinine-based estimating equations in solid-organ transplant recipients. They can be used for clinical management.