D Motta

Comparison between 24‐h proteinuria, urinary protein/creatinine ratio and dipstick test in patients with nephropathy: Patterns of proteinuria in dipstick‐negative patients

Objective. Three main tests are commonly employed for the measurement of proteinuria: the dipstick test, the urinary protein/creatinine ratio (P/C) and the 24‐h urine collection. The aim of this study was to evaluate the correlation between these methods, comparing linear regression and ROC curve data. Material and methods. A total of 297 consecutive outpatients with different renal diseases were included in the study. Twenty‐four‐hour proteinuria was considered the reference test. Results. A high degree of correlation was observed between all the tests (p<0.0001), the highest regression coefficient being between 24‐h proteinuria and P/C (R = 0.82), and the lowest between P/C and the dipstick test (R = 0.72). The dipstick test failed to detect pathological proteinuria in 94 patients (31.6 %). Therefore, in these subjects, the patterns of proteinuria were assessed by immunofixation and sodium dodecyl sulphate (SDS) electrophoresis. Conclusions. Our data strongly support the use of urinary P/C for the detection of proteinuria, at least in nephrology units, where the prevalence of proteinuria is likely to be high.

Low-protein vegetarian diet with alpha-chetoanalogues prior to pre-emptive pancreas-kidney transplantation.

BACKGROUND Pre-emptive pancreas-kidney transplantation is increasingly considered the best therapy for irreversible chronic kidney disease (CKD) in type 1 diabetics. However, the best approach in the wait for transplantation has not yet been defined. AIM To evaluate our experience with a low-protein (0.6 g/kg/day) vegetarian diet supplemented with alpha-chetoanalogues in type 1 diabetic patients in the wait for pancreas-kidney transplantation. METHODS Prospective study. Information on the progression of renal disease, compliance, metabolic control, reasons for choice and for drop-out were recorded prospectively; the data for the subset of patients who underwent the diet while awaiting a pancreas-kidney graft are analysed in this report. RESULTS From November 1998 to April 2004, 9 type 1 diabetic patients, wait-listed or performing tests for wait-listing for pancreas-kidney transplantation, started the diet. All of them were followed by nephrologists and diabetologists, in the context of integrated care. There were 4 males and 5 females; median age 38 years (range 27.9-45.5); median diabetes duration 23.8 years (range 16.6-33.1), 8/9 with widespread organ damage; median creatinine at the start of the diet: 3.2 mg/dl (1.2-7.2); 4 patients followed the diet to transplantation, 2 are presently on the diet, 2 dropped out and started dialysis after a few months, 1 started dialysis (rescue treatment). The nutritional status remained stable, glycemia control improved in 4 patients in the short term and in 2 in the long term, no hyperkalemia, acidosis or other relevant side effect was recorded. Proteinuria decreased in 5 cases, in 3 from the nephrotic range. Albumin levels remained stable; the progression rate was a loss of 0.47 ml/min of creatinine clearance per month (ranging from an increase of 0.06 to a decrease of 2.4 ml/min) during the diet period (estimated by the Cockroft-Gault formula). CONCLUSIONS Low-protein supplemented vegetarian diets may be a useful tool to slow CKD progression whilst awaiting pancreas-kidney transplantation.

The grafted kidney takes over: disappearance of the nephrotic syndrome after preemptive pancreas-kidney and kidney transplantation in diabetic nephropathy

This report describes the rapid and complete reversal of proteinuria after preemptive transplantation in diabetic nephropathy. Case 1 was a 42-year-old woman with type 1 diabetes (before pancreas-kidney graft: serum creatinine 1.6 mg/dL and proteinuria 9.1 g/day; 1 month after pancreas-kidney graft: proteinuria 0.3 g/day and creatinine 1.3 mg/dL). Case 2 was a 48-year-old man with type 2 diabetes (before kidney graft: creatinine 2 mg/dL and proteinuria 5.9 g/day; 1 month after: proteinuria 0.7 g/day and creatinine 1.1 mg/dL). The proteinuria pattern changed (pre: glomerular nonselective, tubular complete; post: physiologic). Renal scintiscan (99mTC-MAG3) demonstrated functional exclusion of the native kidneys, despite high pretransplant clearance (> 50 mL/min). The effect was not linked to euglycemia or readily explainable by pharmacologic effects (no difference in renal parameters after pancreas transplantation with the same protocols). These data confirm the efficacy of preemptive kidney and kidney-pancreas transplantation in diabetic nephrotic syndrome and indicate that a regulatory hemodynamic effect should be investigated.

A Simple Method for the Classification of Proteinuria

We read with interest the paper of Bergon et al. about the classification of renal proteinuria (1) and we agree with the authors that in the presence of proteinuria or diagnosed nephropathy it is indispensable to measure protein excretion rate in a 24-hour urine collection using a dye-binding assay with pyrogallol-red (2, 3). Otherwise, in our experience a correct evaluation of proteinuria typing is a correct and feasible method that leads to a better standardization of the results. Furthermore, the assessment in mid-stream morning second urine samples by a nephelometric analysis of urinary proteins, using urinary protein/creatinine ratios allows a reduction of pre-analytical errors linked to urine time collection and to possible protein digestion by proteases action in 24-hour-stored urine (4). Recent studies shed new light into the physiopathlogical mechanisms of urinary protein excretion: thus, in our opinion a correct method of classification of proteinuria must distinguish not only between glomerular and tubular proteinuria but, in a better way, between selective glomerular proteinuria (presence of albumin and transferrin) and not selective glomerular proteinuria (presence of proteins with MW >100 kDa), and also between incomplete tubular proteinuria (presence of proteins with MW <50 kDa) and complete tubular proteinuria (presence of proteins with MW <23 kDa) (5). Data obtained showed that complete tubular proteinuria was an index of stronger tubular pathological involvement often associated to higher levels of serum creatinine and to a worse outcome (6). In our laboratory we developed an immunofixation method using specific polyclonal antisera, for qualitative/semi-quantitative analysis of urinary proteins (retinol-binding protein: RBP; α1-microglobulin: α1m; albumin; transferrin; immunoglobulin G: IgG and α2-macroglobulin: α2m), allowing a better definition of selectivity of glomerular proteinuria and of complete or incomplete tubular proteinuria (CSI-Nefro Cinque, BIOCI, Turin, Italy) (7). The CSI (Cross Star Immunofixation) method is a gel-immunoprecipitation, characterized by a high analytical sensitivity. This is due to the characteristics of the gel itself, to the mono-specificity of the antisera and to the new type of cross-deposition of the samples and