A novel non-synonymous polymorphism (p.Arg240His) in C4b-binding protein is associated with atypical hemolytic uremic syndrome and leads to impaired alternative pathway cofactor activity

Atypical hemolytic uremic syndrome (aHUS) is a disorder characterized by hemolytic anemia, thrombocytopenia, and acute renal failure. Mutations, polymorphisms, and copy number variation in complement factors and inhibitors are associated with aHUS. In this study, we report the first functional non-synonymous polymorphism in the complement inhibitor C4b-binding protein (C4BP) alpha-chain (c.719G>A; p.Arg240His), which is associated with aHUS. This heterozygous change was found in 6/166 aHUS patients compared with 5/542 normal (chi2 = 6.021; p = 0.014), which was replicated in a second cohort of aHUS patients in which we found 5/170 carriers. The polymorphism does not decrease expression efficiency of C4BP. p.Arg240His is equally efficient as the wild type in binding and supporting degradation of C4BP but its ability to bind C3b and act as cofactor to its degradation both in fluid phase and on surfaces is impaired. This observation supports the hypothesis that dysregulation of the alternative pathway of complement is pivotal for aHUS. Three of the patients carry also mutations in membrane cofactor protein and factor H strengthening the hypothesis that individuals may carry multiple susceptibility factors with an additive effect on the risk of developing aHUS.

Correction of chronic metabolic acidosis for chronic kidney disease patients

BACKGROUND

Metabolic acidosis is a feature of chronic kidney disease (CKD) due to the reduced capacity of the kidney to synthesise ammonia and excrete hydrogen ions. It has adverse consequences on protein and muscle metabolism, bone turnover and the development of renal osteodystrophy. Metabolic acidosis may be corrected by oral bicarbonate supplementation or in dialysis patients by increasing the bicarbonate concentration in dialysate fluid.

OBJECTIVES

To examine the benefits and harms of treating metabolic acidosis in patients with CKD, both prior to reaching end-stage renal disease (ESRD) or whilst on renal replacement therapy (RRT), with sodium bicarbonate or increasing the bicarbonate concentration of dialysate.

SEARCH STRATEGY

We searched CENTRAL (The Cochrane Library, issue 4 2005), Cochrane Renal Group's specialised register (October 2005), MEDLINE (1966 - October 2005) and EMBASE (1980 - October 2005).

SELECTION CRITERIA

Randomised controlled trials (RCTs), crossover RCTs and quasi-RCTs investigating the correction of chronic metabolic acidosis in adults or children with CKD.

DATA COLLECTION AND ANALYSIS

Outcomes were analysed using relative risk (RR) and weighted mean difference (MD) for continuous measures.

MAIN RESULTS

We identified three trials in adult dialysis patients (n = 117). There were insufficient data for most outcomes for meta-analysis. In all three trials acidosis improved in the intervention group though there was variation in achieved bicarbonate level. There was no evidence of effect on blood pressure or sodium levels. Some measures of nutritional status/protein metabolism (e.g. SGA, NP NA) were significantly improved by correction in the one trial that looked in these in detail. There was heterogeneity of the effect on serum albumin in two trials. Serum PTH fell significantly in the two trials that estimated this, there was no significant effect on calcium or phosphate though both fell after correction. Complex bone markers were assessed in one study, with some evidence for a reduction in bone turnover in those with initial high bone turnover and an increase in low turnover patients. The studies were underpowered to assess clinical outcomes, in the one study that did there was some evidence for a reduction in hospitalisation after correction.

AUTHORS' CONCLUSIONS

The evidence for the benefits and risks of correcting metabolic acidosis is very limited with no RCTs in pre-ESRD patients, none in children, and only three small trials in dialysis patients. These trials suggest there may be some beneficial effects on both protein and bone metabolism but the trials were underpowered to provide robust evidence.

Increase in Creatinine and Cardiovascular Risk in Patients with Systolic Dysfunction after Myocardial Infarction

Baseline renal function is a potent independent risk factor for adverse events after acute myocardial infarction (MI). Worsening renal function (WRF) has been shown to influence outcomes in the heart failure population, but its impact on cardiovascular risk in the post-MI period has not been well defined. For assessment of the prognostic importance of WRF, 2231 patients who had left ventricular dysfunction and were enrolled in the Survival and Ventricular Enlargement (SAVE) trial were studied. Patients were randomly assigned between 3 and 16 d (average 11 d) after acute MI to receive captopril or placebo; those with a serum creatinine of >2.5 mg/dl were excluded from SAVE. WRF was defined as an increase in creatinine of >0.3 mg/dl measured from baseline to 2 wk after randomization. The predictive value of WRF on cardiovascular morbidity and mortality was examined during 42 mo of follow-up. Paired serum creatinine measurements at baseline and 2 wk were available in 1854 patients. WRF occurred in 223 (12.0%) patients and was a stronger predictor of death (hazard ratio [HR] 1.46; 95% confidence interval [CI] 1.05 to 2.02) than baseline creatinine (HR 1.31; 95% CI 1.01 to 1.70). WRF also showed an increased risk for cardiovascular death (HR 1.62; 95% CI 1.14 to 2.30) and the composite end point (HR 1.32; 95% CI 1.03 to 1.70). When stratified by treatment, 104 (5.7%) and 116 (6.4%) patients with WRF in the placebo and captopril groups had no significant association between treatment group and WRF (P = 0.38). The risk for death associated with WRF was HR 1.63 (95% CI 1.05 to 2.52) in the placebo group compared with HR 1.33 (95% CI 0.81 to 2.21) in the captopril group (P = 0.49 for interaction). WRF as early as 2 wk after MI was not uncommon (12.0%) and was associated with increased mortality in patients without renal dysfunction at baseline. Patients who received captopril did not demonstrate more WRF than patients who received placebo. Monitoring serum creatinine in patients during the first few weeks after MI may help to identify those who are at highest risk and guide effective long-term therapeutic choices.

Late referral for dialysis: improving the management of chronic renal disease

BACKGROUND

Timely nephrological referral of patients with chronic renal failure (CRF) is important, but referral at a late stage of disease is common.

AIM

To investigate whether late referral of patients is avoidable, and where the missed opportunities lie.

DESIGN

Prospective ascertainment of new cases and comprehensive review of pre-end stage history.

METHODS

Patients admitted to Bristol and Portsmouth renal units for chronic RRT between June 1997 and May 1998 were identified from computer databases. Data were collected from case notes and hospital records, and a self-administered patient questionnaire. Late referral, defined as dialysis within 4 months of first referral to a dialysing nephrologist, was categorized by algorithm as unavoidable or avoidable.

RESULTS

Of 250 patients, 96 (38%) were referred late. Forty-three (45%) had definite avoidable reasons: 35 (37%) with raised serum creatinine for a median 3.7 years (IQR 1.5-8.2) before referral, and eight (8%) with risk factors for renal disease but scant assessment of renal function; 12/43 (31%) had a diagnosis of diabetic nephropathy. Late referred patients were less likely to receive standard renal therapies for chronic renal failure, were in a poorer clinical state at start of RRT, and more often required emergency dialysis, compared to patients referred early. Late referrals were as likely from a hospital as a primary care physician.

DISCUSSION

A significant proportion of patients are avoidably referred to a dialysing renal unit at a very late stage. Guidelines on referral should be developed by nephrologists, primary and secondary care physicians, and patient groups, and further research is needed into the cost-effectiveness of early referral strategies.

The haemolytic uraemic syndrome in patients with AIDS

OBJECTIVE

Thrombotic microangiopathies have been increasingly recognised in HIV infection. The contribution of haemolytic uraemic syndrome (HUS) has not received as much emphasis as other members of the thrombotic microangiopathies. We describe the clinical features and prognosis of HUS in a group of patients with AIDS.

SETTING

St Bartholomew's and The Middlesex Hospitals, London.

PATIENTS

Five HIV seropositive individuals with clinical and histological features consistent with HUS.

INTERVENTIONS

Blood transfusion, fresh frozen plasma, haemodialysis, renal biopsy, autopsy.

CONCLUSIONS

HUS occurs in advanced HIV infection. Hypertension was a prominent clinical feature in HUS in this patient group. Measures to limit renovascular damage were unsuccessful and haemodialysis was usually needed to support renal function. The prognosis is poor, no patient achieved clinical remission and all died.

High incidence of end-stage renal disease in Indo-Asians in the UK

In a retrospective survey, we show that the incidence of end-stage renal disease (ESRD) is significantly raised among immigrant Indo-Asians referred to two UK renal units (p < 0.001). In addition to the expected increase in diabetic nephropathy, glomerulonephritis and chronic pyelonephritis are also seen more frequently in Indo-Asians. The most striking finding was a five-fold increase in ESRD of uncertain cause (p < 0.001) presenting with small smooth kidneys, which was strongly associated with active, mostly non-renal tuberculosis. The causes of this generalized increased susceptibility to renal disease are unknown. These findings have important implications both for primary health care screening and for planning the provision of renal replacement therapy.

The effect of intraperitoneal insulin delivery on carbohydrate metabolism in type 1 (insulin-dependent) diabetic patients

Patients with type 1 diabetes are usually given insulin subcutaneously, but this does not mimic the physiological route of pancreatic insulin release, which may be better achieved with intraperitoneal insulin. Five C-peptide negative type 1 diabetic patients were studied on two occasions, once with intravenous (IV) and once with intraperitoneal (IP) insulin. Normoglycaemia was maintained from 1700 h with variable insulin infusion, and glucose turnover and recycling assessed from 0600 to 0800 h. A 4-h hyperinsulinaemic (25 mU kg-1 h-1) euglycaemic clamp was then performed, with IP or IV insulin delivery. During the night similar insulin infusion rates were needed to achieve equal blood glucose concentrations. Glucose turnover was identical (IV: 2.4 +/- 0.2 vs IP: 2.3 +/- 0.1 mg kg-1 min-1) (+/- SE) with glucose/carbon recycling 8.8 +/- 4.7 and 12.8 +/- 2.9% (NS). Blood lactate, pyruvate and alanine concentrations were significantly higher with IP than IV insulin (P less than 0.05). During the clamp, insulin concentration was 28 +/- 3 mU/l with IV insulin and 15 +/- 1 mU/l with IP insulin (P less than 0.05) and glucose requirement 2.0 +/- 0.5 and 0.8 +/- 0.3 mg kg-1 min-1, respectively (P less than 0.05). Glucose carbon recycling was higher with IP insulin (P less than 0.05). We conclude that: (1) in type 1 (insulin-dependent) diabetic patients hepatic glucose production could be normalized with both routes of insulin administration, and (2) at the same insulin infusion rate, the relative peripheral hypoinsulinaemia with IP route is sufficient to increase the rate of release of gluconeogenic precursors, or decrease their hepatic uptake.