The Sask formula to estimate glomerular filtration rate in renal transplant patients.

The aim of this study was to develop a glomerular filtration rate (GFR) equation for renal transplant and compare its performance with Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and isotope dilution mass spectrometry (IDMS) equations. Using genetic symbolic regression analysis, the Sask equation was developed from a training sample of 772 isotope GFR (iGFR) scans performed in 99 transplanted patients. It was then validated in two other samples of 269 scans with the same number of patients. Standard methods including accuracy at 30% range from reference values were compared. In two validation samples, the Sask equation maintained the lowest bias of -0.7 ± 19.0 and 0.4 ± 18.4 ml/min/1.73 m(2) (p < 0.05) versus -3.1 ± 19.6 and -7.2 ± 18.8 ml/min/1.73 m(2) for CKD-EPI and -2.2 ± 19.2 and -6.5 ± 18.3 ml/min/1.73 m(2) for IDMS, respectively. In those with iGFR between 90 and 30 ml/min/1.73 m(2), the Sask equation demonstrated: (1) the lowest bias of -1.0 ± 15.7 and -0.4 ± 15.7 ml/min/1.73 m(2) (p < 0.05 vs. other tests); (2) an accuracy of 75.5 and 76.1% (p < 0.05 vs. other tests), and (3) a mean percentage error of 1.9 ± 30.5 and -4.1 ± 31.4 ml/min/1.73 m(2) (p < 0.05 vs. other tests). Analysis based on gender demonstrated improved performance in the total and subtotal female populations with GFR between 90 and 30 ml/min/1.73 m(2). The CKD-EPI and Sask equations performed better than IDMS. The Sask equation demonstrated improved bias over CKD-EPI, with iGFR between 90 and 30 ml/min/1.73 m(2), particularly in females.

Prevalence of silent gastrointestinal complications in maintenance renal transplant population.

This study aims to determine the prevalence of silent GI complications within a stable renal transplant population and to investigate whether the conversion to enteric-coated myco-phenolate sodium (EC-MPS, Myfortic) would improve symptom scores. This was a single-center, open-label, non-randomized, prospective study. Patients without any history of GI com-plaints were evaluated by means of the gastrointestinal symptom rating scale (GSRS), with subse-quent switch to EC-MPS in a group of patients. Silent complications were defined as patients who voiced no GI complaints at clinic visits despite a score of > or = 2 on GSRS scale. A total of 236 stable patients participated in the trial. The prevalence of baseline scores > or = 2 was relatively high with abdominal pain 29.66%, reflux 37.28%, indigestion 50%, constipation 58.47% and diarrhea 33.4%. Of 236 patients, 80 were converted to EC-MPS. There was statistically significant improvement on all scales in the subgroup of patients with GSRS score > or = 2 (P < 0.05). In conclusion, the GSRS scale identified a high percentage of silent gastrointestinal complications in this renal transplant population. The converted patients with higher GSRS scores reported a sustained improvement.

Measurement error in estimated GFR slopes across transplant chronic kidney disease stages.

BACKGROUND: This study examines if transplant glomerular filtration rate (GFR) slope prediction is affected by the degree of transplant chronic kidney disease (CKDT) stage. METHODS: Serial changes in estimated GFR (DeltaeGFR) by Cockcroft-Gault (CG) and Modified Diet in Renal Disease-Isotope Dilution Mass Spectrometry (MDRD-IDMS) equations were compared to simultaneous changes in isotope GFR (DeltaiGFR) in renal transplant patients who had at least four scans. RESULTS: Total number of patients (iGFR scans) was 99 (772) while the corresponding numbers in CKDT stages 1-4 were 33 (103), 69 (239), 75 (316) and 37 (96), respectively. Measurement error [(DeltaeGFR - DeltaiGFR) x 100/DeltaiGFR] (median +/- IQR, interquartile range) estimated from CG and MDRD-IDMS slopes were -414.29 +/- 276.16% and -342.86 +/- 210.18% (stage 1); -350.00 +/- 301.22% and -300.00 +/- 525.00% (stage 2); -26.02 +/- 404.38% and -26.58 +/- 423.13% (stage 3); 10.26 +/- 142.18% and -76.92 +/- 145.64% (stage 4), respectively. The proportion of patients with CG measurement error < or =1-fold in stages 1 and 2 of 12 and 14.5% was significantly (p < 0.05) lower than that of 36.3 and 52.8% at stages 3 and 4, respectively. Similar measurement errors were observed for MDRD-IDMS. CONCLUSIONS: Transplant GFR slope prediction is affected by the degree of renal dysfunction. Errors in slope prediction are much higher in those with better function and thus add another limitation for eGFR use in longitudinal studies on progressive graft dysfunction.

Comparing measures of cystatin C in human sera by three methods.

BACKGROUND: Cystatin C (Cys C) is measured by particle-enhanced nephelometric immunoassay (PENIA), particle-enhanced turbidimetric immunoassay (PETIA) and ELISA. AIM: To determine differences among these methods. METHOD: 80 normal human sera and 20 from patients with renal and/or heart disease were simultaneously assayed. Statistical analyses including receiver operating characteristics (ROC) of the three methods were compared. RESULTS: There was a highly significant correlation across the assay range between the ELISA and PENIA (r(2) = 0.94) and PETIA methods (r(2) = 0.95). Analysis of variance and bias were poor between the ELISA and the other two methods. Mean difference between ELISA and PETIA was 0.65 +/- 0.63 microg/ml, while it was 0.58 +/- 0.53 microg/ml between ELISA and PENIA. Accuracy (at 30% range) was 17 and 11% between ELISA and PETIA and ELISA and PENIA, respectively. Normalization of the ELISA by a factor of 0.66 improved this relationship. AUC of ROC curves of PENIA, ELISA and normalized ELISA to predict Cys C levels measured from PETIA were all above 0.87 (p = not significant between curves). Criterion values of ELISA*.66 method was close to PETIA measurements. CONCLUSION: There is a significant difference in measured human Cys C levels among the three methods, and normalization of ELISA narrows these differences.

Validation of the Virga GFR equation in a renal transplant population.

BACKGROUND: Virga and colleagues derived a glomerular filtration rate (GFR) equation which demonstrated a superior performance over Cockcroft-Gault (C-G) and modified diet in renal disease-isotope dilution mass spectrometry (MDRD-IDMS) formulas in chronic kidney disease (CKD) patients. AIM: To validate the performance of the Virga equation on 103 renal transplant patients. METHODS: We compared the performances of the MDRD-IDMS, C-G and Virga equations using inulin clearance as a reference test. Error, accuracy, relative accuracy, precision, scatter, and coefficient of variance of each equation were tested. RESULTS: The mean absolute percentage error in estimated GFR by the new equation was 39.8 +/- 36.34% (mean +/- SD). Relative accuracy at 10, 30 and 50% range were 18.44, 48.54 and 73.78%, respectively. It has a bias of 0.09 +/- 0.169 and a precision of 19.69. Inulin clearance (GFR) in stages 1-4 were 106.19 +/- 14.11, 71.17 +/- 7, 42.37 +/- 8.40 and 22.92 +/- 3.48 ml/min/1.73 m(2), respectively. Comparative statistics in the overall population and in patients with transplant CKD stage 3T showed that the MDRD-IDMS equation had better accuracy. The performance of MDRD-IDMS over the Virga equation was clearly superior for males. In patients with CKD stage 2T, the Virga equation showed superiority over MDRD-IDMS. In the overall and subpopulations, the Virga equation performed better than the C-G equation. CONCLUSION: Among renal transplant patients, the results suggest that the best GFR estimate is probably obtained using the MDRD-IDMS equation in moderate kidney failure whilst the Virga formula was superior to MDRD-IDMS for patients with mild kidney failure. As in untransplanted patients, estimating GFR with the MDRD-IDMS equation is not advisable in the range of normal renal function because of its known underestimation of renal function.

Accuracy to estimate rates of decline in glomerular filtration rate in renal transplant patients.

BACKGROUND: We examined the use of the Cockroft Gault (C-G) test, Modified Diet in Renal Disease 2 (MDRD2) test, and inverse serum creatinine (Delta1/Scr) to estimate rates of decline in renal transplant function using isotope glomerular filtration rate (GFR) as a reference test. METHODS: Percent changes in estimated GFR (DeltaeGFR) were compared to simultaneous changes in isotope GFR (DeltaiGFR) in 72 patients. RESULTS: The number of iGFR was 508 with a mean of 7.15+/-3.15 scans per patient. There was a decline in iGFR of 16.14+/-21.37 ml/min over the study duration of 88.9+/-57.6 months. DeltaeGFR and Delta1/Scr correlated significantly with DeltaiGFR. Accuracy to predict DeltaiGFR from the eGFRs was limited to <65% concordance within 30% range from changes in iGFR. Slope analyses showed a significantly lower percent annual loss in mean iGFR of 6.03% than that of the C-G of 8.62% and MDRD2 of 8.96% (P<0.001). The within patient variability measured from the standard deviation (ml/min) of root mean square of 4.69 for iGFR was significantly higher than that for C-G and MDRD2 of 2.46 and 2.94, respectively. iGFR and eGFR at first observation correlated significantly (P<0.001) with last observation. CONCLUSIONS: iGFR is significantly more variable within patient than the other predictors, and the two estimators predict the iGFR with a high sensitivity but low specificity. This is a clinically reasonable combination. Predicted percent of annual loss in iGFR appears to be smaller than that using the two estimators.