Christopher J. Deighan

Early Initiation of Dialysis Fails to Prolong Survival in Patients with End-Stage Renal Failure

ABSTRACT. There is a trend to start dialysis earlier in patients with chronic renal failure. Studies that suggest improved survival from earlier initiation of dialysis are flawed in that they have measured survival from start of dialysis rather than from a time point before dialysis, when patients have the same renal function. This flaw is termed lead-time bias. Using the electronic patient record at the renal unit of Glasgow Royal Infirmary, all patients were identified who had received dialysis for chronic renal failure and who had sufficient data to calculate the time point at which they reached an estimated creatinine clearance (eC Cr ) of 20 ml/min ( n = 275). This date was used to time survival. The patients were divided into early and late start groups by the median eC Cr for all patients at initiation of dialysis, which was 8.3 ml/min. There was no significant benefit in patient survival from earlier initiation of dialysis. A Cox proportional hazards model demonstrated a significant inverse relationship between eC Cr at start of dialysis and survival (hazard ratio, 1.1; P = 0.02), i.e. , patients who started dialysis with a lower eC Cr tended to survive longer. This relationship retained significance when gender, age, weight, presence of diabetes, mode of first dialysis, initial dialysis access, hemoglobin, serum albumin, blood leukocyte count, Wright/Khan index, and eC Cr at the start of dialysis were taken into account. This study fails to support a policy of earlier initiation of dialysis for patients with end-stage renal failure.

Atherogenic lipoprotein phenotype in end-stage renal failure: Origin and extent of small dense low-density lipoprotein formation

End-stage renal failure (ESRF) is associated with dyslipidemia and accelerated atherosclerosis. Triglyceride-rich lipoproteins accumulate and qualitative changes take place in low-density lipoprotein (LDL), with a predominance of the small dense LDL phenotype. Increased small dense LDL (LDLIII) is a known risk factor for cardiovascular disease. To assess the extent of LDLIII formation in ESRF and identify factors contributing to LDLIII production, we analyzed LDL subfractions by density-gradient ultracentrifugation, very low-density lipoprotein subfractions, and lipase activity in 75 patients with ESRF (25 hemodialysis [HD], 25 peritoneal dialysis [PD], and 25 predialysis patients) and 40 age- and sex-matched controls. The percentage of LDLIII was increased in all three patient groups compared with controls (PD, 33% +/- 29% [mean +/- SD]; P < 0.005; HD, 30% +/- 22%; P < 0.01; predialysis, 26% +/- 26%; P < 0.01; all versus controls, 14% +/- 10%). Plasma LDLIII concentration was increased only in PD patients (median, 84 mg/dL; interquartile range [IQR], 29 to 160 mg/dL versus controls; median, 31 mg/dL; IQR, 26 to 54 mg/dL). In other patient groups, total LDL level was less, with heterogeneity in LDLIII concentrations. Forty percent of PD patients and 28% of HD and predialysis patients had LDLIII concentrations greater than 100 mg/dL compared with 2.5% of controls (P = 0.002). Plasma triglyceride levels (r(2) = 38.4%; P < 0.001) and hepatic lipase activity (r(2) = 6.7%; P < 0.03) were independent predictors of LDLIII concentration. The strong association between LDLIII concentration and triglyceride level was present in all three patient groups (HD, r(2) = 47.9%; PD, r(2) = 45. 2%; predialysis, r(2) = 25.8%); plasma triglyceride levels greater than 177 mg/dL (2.0 mmol/L) had an 86% specificity and 79% sensitivity for predicting an LDLIII concentration greater than 100 mg/dL. We conclude that the atherogenic lipoprotein phenotype predominates in ESRF, with excess LDLIII particularly prominent in PD patients. Atherogenic levels of LDLIII are found in patients with triglyceride levels greater than 177 mg/dL. This is likely to represent a further cardiovascular risk factor in this population.

Assessing proteinuria in chronic kidney disease: protein–creatinine ratio versus albumin–creatinine ratio

BACKGROUND Quantification of proteinuria is important in the assessment of chronic kidney disease (CKD). The aim of this study was to investigate the optimal test to identify significant proteinuria. METHODS We retrospectively assessed the relationship between total protein:creatinine ratio (TPCR), albumin:creatinine ratio (ACR) and 24-h urine total protein in 6842 patients with CKD focusing on performance at thresholds of 0.5 and 1 g/day of proteinuria. RESULTS The relationship between ACR and TPCR is non-linear. TPCR is highly correlated with 24-h urine protein (Spearmans rho = 0.91), though ACR also performs well (rho = 0.84). Using receiver-operator characteristic curve analysis, TPCR outperforms ACR at predicting 0.5 g/day [area under the curve (AUC) 0.967 vs 0.951, P < 0.001] and 1 g/day of proteinuria (AUC 0.968 vs 0.947, P = 0.004). A TPCR threshold of 100 mg/mmol had a higher sensitivity (94% vs 79%) but lower specificity (88% vs 95%) than an ACR of 70 mg/mmol to predict 1 g/day of total proteinuria. To achieve comparable sensitivity, the ACR threshold falls to 17.5 mg/mmol, with lower specificity than TPCR (69.8%). Sensitivity of TPCR rose with increasing age, and in females: to achieve 95% sensitivity in a man <49 years, requires a TPCR of 65 mg/mmol, compared to 179 mg/mmol in a woman >79 years. Non-albumin proteinuria was a lower proportion of total proteinuria in patients receiving angiotensin-converting enzyme inhibitors or angiotensin receptor blockade than in those who were not (P < 0.001). CONCLUSIONS TPCR is a more sensitive screening test than ACR to predict clinically relevant proteinuria. The diagnostic performance of both tests varies substantially with age and gender, and should be taken into consideration when interpreting results. Total proteinuria cannot be adequately predicted from ACR, and our results suggest that caution is appropriate before utilizing ACR in patients with non-diabetic CKD.

Comparison of Urinary Albumin and Urinary Total Protein as Predictors of Patient Outcomes in CKD

BACKGROUND Proteinuria is common and is associated with adverse patient outcomes. The optimal test of proteinuria to identify those at risk is uncertain. This study assessed albuminuria and total proteinuria as predictors of 3 patient outcomes: all-cause mortality, start of renal replacement therapy (RRT), and doubling of serum creatinine level. STUDY DESIGN Retrospective longitudinal cohort study. SETTING & PARTICIPANTS Nephrology clinic of a city hospital in Scotland; 5,586 patients with chronic kidney disease (CKD) and proteinuria measured in random urine samples (n = 3,378) or timed urine collections (n = 1,808). PREDICTORS Baseline measurements of albumin-creatinine ratio (ACR), total protein-creatinine ratio (PCR), 24-hour albuminuria, and total proteinuria. OUTCOMES All-cause mortality, start of RRT, and doubling of serum creatinine level were assessed using receiver operating characteristic curves and Cox proportional hazards models. MEASUREMENTS Blood pressure, serum creatinine level, ACR, PCR, date of death, date of starting RRT. RESULTS Patients were followed up for a median of 3.5 (25th-75th percentile, 2.1-6.0) years. For all outcomes, adjusted HRs were similar for PCR and ACR (derived from random urine samples and timed collections): death, 1.41 (95% CI, 1.31-1.53) vs 1.38 (95% CI, 1.28-1.50); RRT, 1.96 (95% CI, 1.76-2.18) vs 2.33 (95% CI, 2.06-3.01); and doubling of serum creatinine level, 2.03 (95% CI, 1.87-2.19) vs 1.92 (95% CI, 1.78-2.08). Receiver operating characteristic curves showed almost identical performance for ACR and PCR for the 3 outcome measures. Adjusted HRs for ACR and PCR were similar when derived from random urine samples or timed collections and compared with 24-hour total protein and albumin excretion for each outcome measure. LIMITATIONS This is a retrospective study. CONCLUSIONS Total proteinuria and albuminuria perform equally as predictors of renal outcomes and mortality in patients with CKD. ACR and PCR were as effective as 24-hour urine samples at predicting outcomes and are more convenient for patients, clinicians, and laboratories. Both ACR and PCR stratify risk in patients with CKD.

Risk Factors for Restless Legs Syndrome in Dialysis Patients

Background: Restless legs syndrome (RLS) is a movement disorder that affects 6.6–62% of dialysis patients. The aims of this multicentre cross-sectional study were to document the frequency, prevalence and severity of RLS in patients attending 5 dialysis centres for chronic hospital haemodialysis (HHD) and to identify associated risk factors. Methods: Thediagnosis of RLS was made using the criteria of The International Restless Legs Study Group. The following data were collected: age; gender; duration of renal replacement therapy (RRT); current smoking status; urea reduction ratio; weekly erythropoietin dose; weekly intravenous iron dose; prescribed beta blocker; prescribed renin/angiotensin system inhibitors and pre-dialysis blood concentrations of haemoglobin, ferritin, total calcium (corrected for albumin), albumin, phosphate, parathyroid hormone. Associations with RLS were analysed by univariate and multivariate logistic regression. Results: Data relating to 277 of 295 patients who had been attending for regular HHD for >3 months were collected. RLS was present in 127 (45.8%). 82 (29.6%), 27 (9.7%) and 18 (6.5%) patients had mild, moderate and severe RLS, respectively. 39 patients (14.1%) were prescribed medicines aimed at reducing RLS. 30 (76.9%) of these 39 patients still had RLS. Female gender (RR 2.17; p = 0.01), increasing duration since first dialysis (RR 1.06 per year; p = 0.03) and increasing body weight(RR 1.02 per kg; p = 0.02) were independent risk factors for RLS by multivariate analysis. In contrast to previous studies, we found no association with iron status, haemoglobin, serum phosphate or smoking. Conclusions: There is a high prevalence of RLS in our population and therapeutic intervention appears to have limited efficacy. The associations with female gender, duration of RRT and body weight deserve further study.

The atherogenic lipoprotein phenotype: small dense LDL and lipoprotein remnants in nephrotic range proteinuria

The dyslipidaemia in nephrotic-range proteinuria is believed to contribute to the increased atherogenesis associated with the condition. Excess small dense low density lipoprotein (LDLIII) contributes to this risk. Lipoprotein remnants (RLP) may also be implicated but have not been studied in this population. We measured the plasma concentration of low density lipoprotein (LDL) subfractions (by density gradient ultracentrifugation), RLP (by immunoaffinity gel), very low density lipoprotein (VLDL) subfractions, post heparin lipases and cholesteryl ester transfer protein (CETP) activity in 27 patients with glomerular disease and albuminuria >2.0g. These were compared with 27 age and sex matched controls. Proteinuric patients had increased LDLIII concentration (patients 182 (84:267) vs. controls 31 (27:62); P<0.0001) with reduced lighter LDLI (36 (24:43) vs 69 (46:101); P<0.0005) and LDLII (124 (79:220) vs 178 (129:236); P<0.04, all mg/dl, median+interquartile range). RLP-cholesterol (RLP-C) and triglyceride (RLP-TG) were increased in proteinuric patients (RLP-C 18.9 (11.0:26.9) vs 7.7 (6.0:8.8); P<0.0001, RLP-TG 35.8 (11.8:54.7) vs. 7.2 (4.3:10.0); P<0.0001, all mg/dl). Increased LDLIII and RLP were independent of renal function. VLDL(1) and VLDL(2) concentrations were increased by 258 and 260% (both P<0.0001). CETP activity was increased by 46% (P<0.005). Lipoprotein and hepatic lipase activities did not differ from control values. LDLIII concentration (r(2)=45.7%, P<0.001), RLP-C (r(2)=85.2%, P<0.001) and RLP-TG (r(2)=87.5%, P<0.001) all correlated positively with plasma triglyceride. Moreover, increased LDLIII was associated with both RLP-C (r(2)=31.3%, P<0.002) and RLP-TG (r(2)=33.6%, P<0.002). Excess LDLIII and RLP are present in nephrotic-range proteinuria and add to the spectrum of cardiovascular risk factors present in proteinuric patients. Increases in LDLIII and RLP are closely related to plasma triglyceride. The association between excess RLP and LDLIII suggests that RLP contribute to the increased atherogenicity attributed to the atherogenic lipoprotein phenotype.

Urinary transferrin, high molecular weight proteinuria and the progression of renal disease.

AIMS Proteinuria predicts rate of progression in a variety of nephropathies. There is considerable evidence that iron-transferrin is toxic to proximal tubular cells in vitro, and recent clinical work suggests that selectivity of proteinuria influences the outcome of renal disease. The aim of this study was to examine the relationship between the nature of proteinuria and progression of renal disease. METHODS This was a prospective, cross-sectional study in 66 patients with primary glomerulonephritis, diabetic nephropathy and a variety of other renal diseases. Urinary transferrin was measured by sandwich ELISA and correlated with rate of change in estimated creatinine clearance (ECC). Urinary SDS-PAGE was undertaken to divide proteinuria into tertiles according to molecular weight and to quantify the protein in each tertile. The magnitude of each tertile was then correlated with rate of change in ECC over a median period of 20 months. RESULTS Rate of change of renal function correlated with total proteinuria (r2 = 18%, p < 0.001) and albuminuria (r2 = 17%, p < 0.001), but not urinary transferrin (r2 = 0%, p = 0.235). On univariate analysis high molecular weight proteinuria (r2 = 21%, p < 0.001), intermediate molecular weight proteinuria (r2 = 15%, p = 0.001) and low molecular weight proteinuria (r2 = 10%, p = 0.005) correlated with rate of change in ECC as did total fasting cholesterol (r2 = 7%, p = 0.003). On multivariate analysis, however, the only independent predictors of rate of change in ECC were high molecular weight proteinuria (r2 = 19%, p < 0.001), and total fasting cholesterol (r2 = 5%, p = 0.035). CONCLUSIONS We found no evidence to support the hypothesis that iron-transferrin is important in the development of human renal injury. High molecular weight proteinuria correlates more strongly with rate of progression of renal disease than intermediate molecular weight, low molecular weight or even total proteinuria. This suggests either, that one or more high molecular weightproteins are implicated in causing progressive renal impairment, or that loss of size selectivity at the glomerular basement membrane is associated with accelerated tubulointerstitial damage.

A Prospective Open-Label Randomised Trial of Quinapril and/or Amlodipine in Progressive Non-Diabetic Renal Failure

Background: Treatment of hypertension slows the progression of non-diabetic nephropathies, but the optimal regimen is unknown. Angiotensin-converting enzyme inhibitors are more effective than β-blockers, but their merits relative to calcium channel blockers are less clear. Methods: 73 hypertensive patients with progressive non-diabetic nephropathies were prospectively randomised to open-label quinapril (Q, n = 28), amlodipine (A, n = 28) or both drugs (Q&A, n = 17). Therapy was increased to achieve a diastolic blood pressure <90 mm Hg. Patients were followed for 4 years or until death. The primary outcome was the combined endpoint of doubling serum creatinine, starting renal replacement therapy or death. Results: There was no significant difference in the primary outcome, or in the change of glomerular filtration rate. Blood pressure was equally controlled throughout the study period. 29 (40%) patients were withdrawn from the allocated therapy (Q 39%, A 36%, Q&A 47%). Because of the large crossover between trial arms, the data were re-analysed per protocol. The effect on preventing the need for renal replacement therapy then approached significance between the groups (p = 0.089) and the combined quinapril-containing groups were less likely than the amlodipine group to achieve the primary endpoint (p = 0.038), or the individual endpoints of renal replacement therapy (p = 0.030) or doubling creatinine (p = 0.051). Conclusions: Quinapril is more effective than amlodipine at reducing the incidence of dialysis in patients with progressive renal failure, but only if they can tolerate the drug. The tolerability of these drugs in patients with advanced renal failure is poor.

The link between circulating markers of endothelial function and proteinuria in patients with primary glomerulonephritis

INTRODUCTION It is well established that there is an increase in the incidence of cardiovascular mortality in patients with proteinuric renal disease. The magnitude of the increase in risk is unlikely to be explained by traditional risk factors for cardiovascular disease alone. Proteinuria itself may constitute an additional risk factor, and proteinuric patients are known to have a degree of endothelial dysfunction. The nature of this relationship between proteinuria and endothelial function is the subject of intense investigation. AIM The aim of this study was to examine the relationship between proteinuria and endothelial dysfunction, as reflected by serum von Willebrand factor (vWF), and the soluble cell adhesion molecules VCAM and ICAM, in patients with primary glomerulonephritis (GN). A secondary aim was to discern whether any relationship could be explained by renal function, lipid profile, inflammation or blood pressure. METHODS A cross-sectional study was undertaken in consecutive patients attending a general nephrology clinic with biopsy-proven primary GN. Patients with end-stage renal disease (ESRD), those on immunosuppressive drugs, or with intercurrent infective illnesses were excluded. Blood pressure and body mass index were recorded. Routine lab assays were undertaken for serum creatinine, lipid profile, and 24-hour urinary protein (U(Prot)). Additional serum samples were stored at -80 degrees C for subsequent measurement of vWF, VCAM, ICAM and sensitive C reactive protein (sCRP). RESULTS Data were collected from 129 (86 male) patients. Mean (standard deviation) estimated creatinine clearance was 64 (32) ml/min, and median (interquartile range) 24-hour proteinuria was 1.1 (0.22-2.9) g. Mean vWF was 173 (68) IU/dl, median VCAM, ICAM and sCRP were 594 (410-708) ng/ml, 235 (208-286) ng/ml, and 2.33 (0.83-5.68) mg/l, respectively. There was a significant positive correlation between vWF and U(Prot) (Spearman rank correlation, r = 0.41, p < 0.001). When split into tertiles, according to U(Prot) (0-500 mg, 500-2000 mg, and > 2000 mg), there was a significant, stepwise increase in mean vWF (p < 0.001), log VCAM (p < 0.001), and log ICAM (p = 0.002). On multivariate analysis with vWF as the continuous dependent variable, U(Prot), age, total cholesterol and sCRP were the only significantly independent correlates (model-adjusted R2 = 33%). CONCLUSION In patients with primary GN, there is a significant association between endothelial activation as reflected by vWF, VCAM, or ICAM and increasing proteinuria. Elevations in vWF, as well as being related to classical risk factors, are associated with increases in total proteinuria and low-grade inflammation. Thus, future prospective studies should examine the extent to which vWF and other circulating markers of endothelial activation predict coronary heart disease risk in patients with proteinuric renal disease.

Omega-3 fatty acids improve postprandial lipaemia in patients with nephrotic range proteinuria

BACKGROUND Patients with nephrotic range proteinuria have a marked increase in the risk of cardiovascular disease. Qualitative and quantitative changes in lipids and lipoproteins contribute to this increased risk with an abundance of atherogenic triglyceride (TG) rich apolipoprotein B containing lipoproteins. TG rich lipoproteins predominate postprandially and are associated with increased risk of coronary heart disease (CHD). Omega-3 fatty acids derived from fish oils have been shown to have beneficial effects on lipids and lipoproteins in patients without proteinuria. METHODS 17 patients with nephrotic range proteinuria and 17 age and sex matched controls were studied. Postprandial lipaemia was assessed in patients and controls, before and after 8 weeks treatment with 4 g daily of omega-3 fatty acids (Omacor). A standard fat load (90 g) was administered and blood sampling was performed in the fasting state and at 2, 4, 6 and 8h after the fat load. Chylomicrons and VLDL(1) density fraction was isolated from plasma by density ultracentrifugation. Postprandial chylomicron and VLDL(1) triglyceride concentrations were measured and quantified using the incremental area under the curve (AUC) method. RESULTS Baseline postprandial chylomicron TG AUC was greater in patients compared with controls: median 18.5 mmol/lh (interquartile range 8.9-32.6) vs 9.3 mmol/lh (4.8-14.4) p=0.05. Following treatment patient chylomicron AUC fell [mean reduction 6.8 mmol/lh (95% CI 0.1-13.6) p=0.05]. No significant reduction in chylomicron AUC was observed in the controls [mean reduction 3.9 mmol/lh (95% CI -3.6 to 11.5)]. As a result, following 8 weeks treatment with omega-3 fatty acids, patient and control chylomicron AUC were no longer significantly different [patients 13.5 mmol/lh (7.4-22.9), controls 7.2 mmol/lh (4.6-14.5) both median and IQR, p=nsd]. VLDL(1) TG AUC did not differ at baseline between patients and controls. Furthermore, there was no significant effect on VLDL(1) AUC following treatment in either group. CONCLUSIONS We have shown that there is an excess of postprandial chylomicron density fraction in patients with nephrotic range proteinuria, which is reduced by treatment with omega-3 fatty acids. We suggest that this would be an ideal therapy in combination with statins for this high risk group of patients.