Screening for CKD with eGFR: doubts and dangers

The early identification of chronic kidney disease (CKD) is a legitimate enterprise if it provides meaningful opportunities for effective and safe interventions that reduce the risk of death, end-stage renal disease, or complications of renal dysfunction. The screening of unselected populations not already known to be at risk of CKD has the potential of harm and has not been shown to be cost-effective. The application of formulas for the estimation of GFR (eGFR) to the guidelines for staging of chronic kidney disease (Kidney Disease Outcomes Quality Initiative, K/DOQI) as universal screening tools is of dubious value and has inherent dangers. This conclusion is based both on the unreliability of current formulas for determining eGFR and flaws in the K/DOQI schema for staging of CKD. The failure to take into account the normal age- and gender- associated decline in GFR and the lack of a requirement for other evidence of kidney disease in CKD stage 3 leads to an erroneous categorization of large numbers of mostly elderly and female subjects as having an intermediate stage of a lethal disease. Criteria for CKD staging should take into account the percentile distribution of eGFR by age and gender. Targeted screening for CKD is likely to be more cost-effective than universal screening. Whether early identification and treatment of subjects with "reduced" levels of GFR within the normal range for their age/gender, but without any other manifestations of kidney disease, will reduce the subsequent risk of cardiovascular events or progression to end-stage-renal disease is currently unproven.

The global burden of chronic kidney disease: how valid are the estimates?

BACKGROUND/AIMS

The values for the global prevalence of chronic kidney disease (CKD) are poorly understood. Current classification schemas may overstate the prevalance of CKD. This minireview analyzes the pitfalls in the use of current classification approaches for identifying CKD on a global basis.

METHODS

Literature review and comment.

RESULTS

Published estimates for the global burden of CKD are likely to be incorrect and inflated. Overestimations of prevalence have occurred due to flaws in the classification systems employed and in ascertainment methods.

CONCLUSIONS

A revision of the current system of diagnosing and classifying CKD is needed in order to determine with greater precision true global burden of CKD. A new system is proposed.

Prophylactic Anticoagulation in Nephrotic Syndrome: A Clinical Conundrum

It has long been recognized that nephrotic syndrome is associated with an increased risk for thromboembolic complications, including deep venous thrombosis, renal vein thrombosis, and pulmonary embolism. This risk varies with the nature of the underlying disease and seems to be greatest for membranous nephropathy. Other factors, including the level of serum albumin, previous thromboembolic episodes, and a genetically determined predisposition to thrombosis, may also be involved. Prevention of thromboembolic events with oral anticoagulants in nephrotic syndrome requires a careful case-by-case analysis of the risks for thromboembolic events balanced by the risks for anticoagulant induced bleeding. Markov-based decision analysis using literature-based assumptions regarding these risks has suggested that prophylactic anticoagulants may be indicated in certain circumstances. Such decisions need to take into account the nature of the underlying disease, the severity of the nephrotic syndrome (as assessed by serum albumin concentration), preexisting thrombophilic states, and the overall likelihood of serious bleeding events consequent to oral anticoagulation (as assessed by the international normalized ratio for prothrombin time). The optimal duration of prophylactic anticoagulation is unknown but very likely extends to the duration of the nephrotic state per se.

Rosuvastatin: an independent analysis of risks and benefits

BACKGROUND

Although the effectiveness of statins is well established, analyses of spontaneous adverse event reports have recently questioned the safety of rosuvastatin.

METHODS AND RESULTS

We evaluated the risks and benefits of rosuvastatin and compared it with other statins presently on the market. Information was obtained from a search of medical and scientific literature that produced 3001 entries, of which 591 publications containing particularly relevant data were identified, and from the US Food and Drug Administration (FDA) Adverse Events Reporting System (AERS) and Spontaneous Reporting System through June 30, 2004. For the AERS data and to control for overreporting in the first postmarketing year and the effect on reporting due to the withdrawal of cerivastatin in 2001, we used the rate of a given adverse event among all adverse events as a measure of risk. We found that adverse effects of rosuvastatin in skeletal muscle, liver, and kidney function did not substantially differ in frequency from those reported for those of other statins in the market in 2004, except for the uncommon development of a mild form of presumably "tubular" proteinuria at doses of 40 mg/day or greater. In contrast, cerivastatin had significantly higher rates of myopathy and rhabdomyolysis than rosuvastatin's, but there was no additional effect on renal failure beyond that mediated through rhabdomyolysis. From our literature review, we found that rosuvastatin reduces abnormal lipids on a milligram-per-milligram comparison more than atorvastatin.

CONCLUSION

We conclude that rosuvastatin at approved doses incurs no greater risk for adverse events than other marketed statins, except for a mild form of tubular proteinuria when doses at or above the maximum recommended levels (> or = 40 mg/day) were administered. Its risk-benefit ratio is acceptable when compared with other statins on the market in 2006.

The early history of chemical immunosuppression: 1900-1965

This is a short review on chemical immunosuppression following the discovery of anaphylaxis by Charles Richet. The paper discusses the role of serendipity in the advent of 6-mercapthopurine (6-MP) therapy and the productivity in the field through Nobel Prize recipients.

Why is proteinuria an ominous biomarker of progressive kidney disease?

Progressive tubule injury and interstitial fibrosis frequently accompany glomerulopathies associated with proteinuria. Clinical experience indicates that higher levels of proteinuria prior to, as well as after initiation of treatment predict more rapid decline in renal function and more pronounced tubulointerstitial injury. It has been proposed that filtration of potentially tubulotoxic plasma proteins is responsible for the observed correlations between proteinuria and progression (i.e., proteinuria is a cause and not only a consequence of progressive renal injury). Numerous attempts have been made to identify the species of putative tubulotoxic proteins in this progressive injury process, but much uncertainty persists. These uncertainties stem from nonphysiologic exposure of apical cell surfaces to proteins in vitro, the extremely high concentrations of various proteins tested in vitro, and the nonuniformity of end points measured. Furthermore, there is often a lack of correlation between in vitro and in vivo findings, and a lack of uniformity of results even for seemingly similar in vitro experiments. Less controversy is evident in the potential pathways whereby injured tubules evoke a tubulointerstitial inflammatory and fibrotic response, with many in vivo models serving to incriminate excessive cytokine and chemokine production, infiltration of various inflammatory cells, and the balance between apoptosis and cell proliferation. Despite many years of concerted efforts, we believe it is still unclear whether proteinuria is a cause (and if so, which species of protein), or only a consequence of progressive renal injury. Nevertheless, pending the resolution of these uncertainties by more decisive and unambiguous experimentation, the strongly predictive inverse relationship between level of proteinuria and long-term renal survival currently justifies aggressive antiproteinuric treatment strategies, with a goal of reducing protein excretion rate to the lowest level possible without the induction of symptoms or undue risk.

The rising tide of end-stage renal disease: what can be done?

The prevalence of end-stage renal disease (ESRD) is rising throughout the developed and developing world, although the rate of increase may be attenuating in some regions. Type 2 diabetes mellitus, often a consequence of obesity and accompanied by the metabolic syndrome, is a major cause of progressive renal disease and the increasing global burden of ESRD. Strategies that are cost-effective and applicable at the community level are urgently needed to stem the tide of both type 2 diabetes and the resulting ESRD. Primary and secondary prevention measures, involving screening and interventions, have demonstrated beneficial effects when appropriately designed and targeted to "high-risk" groups. If these strategies can be implemented at the societal level and compliance with the interventions is robust, it is entirely possible that the rising tide of ESRD can be converted into a receding tide of ESRD in the future.

Secondary minimal change disease

The great majority of patients identified as having a 'minimal change lesion' accompanying the nephrotic syndrome have a primary or 'idiopathic' disorder. Nevertheless, it is quite apparent that a similar or identical lesion can appear consequent to a growing number of underlying diseases; it is then known as 'secondary minimal change disease'. The predisposing conditions include neoplastic diseases, toxic or allergic reactions to drugs, infections, auto-immune disorders and other miscellaneous entities. These disorders are reviewed and catalogued in this contribution.

Diagnosis and natural course of membranous nephropathy

Membranous nephropathy is a relatively common glomerular disease found to underlie both nonnephrotic and nephrotic proteinuria. In adults, about 75% of cases are primary (idiopathic) and 25% are secondary to a wide variety of causes, including neoplasia, infections, autoimmunity, and drugs. Presenting features are not distinctive enough to permit a diagnosis without a renal biopsy examination. Serologic studies are normal in the idiopathic disorder. The morphologic features are characteristic and include gradual thickening of the capillary wall caused by the in situ deposition of immune complexes accompanied by new basement membrane synthesis. The natural history of the untreated disorder is variable. Spontaneous remissions (complete and partial) of proteinuria, usually accompanied by stable renal function, eventually occur in 40% to 50% of patients and the remainder slowly progress to end-stage renal disease (ESRD) or die of complications or from unrelated disease after 5 to 15 years. Factors associated with a progressive course include older age at onset, male gender, persisting hypertension, hyperlipidemia and/or hypoalbuminemia, reduced renal function at discovery, persisting nephrotic range glomerular proteinuria, concomitant tubular proteinuria, and advanced glomerular damage with chronic tubulointerstitial fibrosis.

L-carnitine use in dialysis patients: is national coverage for supplementation justified? What were CMS regulators thinking--or were they?

Careful review of all available clinical trials of L-carnitine leads to the conclusion that there is insufficient evidence to support the routine use of L-carnitine for any indication in dialysis patients. The literature suffers from a lack of adequately designed studies, and many of the studies which supposedly justify payment for L-carnitine supplementation are more than 10 years old. While some studies support a subjective improvement in symptoms after a few months of L-carnitine treatment, there is little confirming objective data. Biochemical parameters show minimal, if any, improvements. A major criticism is that many of the reported symptoms could be attributable to anemia, which at the time the L-carnitine studies were taking place, was generally being corrected with EPO. On the other hand, there is little data to support the hypothesis that L-carnitine enhances the response to EPO or overcomes EPO resistance. The decrease in the use of L-carnitine in the past several years may be related in part to difficulty with reimbursement. The decrease also suggests that practitioners have abandoned the hypothesis that L-carnitine supplementation provides substantial clinical benefits, and therefore no longer prescribe it for dialysis patients. For those physicians who plan to prescribe L-carnitine based on the recent CMS reimbursement decision, it must be remembered that the laboratory measurement of free carnitine may be difficult and inaccurate. For those patients with private insurance, payment for the lab test is out of pocket. If the free carnitine level is measured once dialysis starts, a value in the CMS "deficient" range can occur since carnitine drops early in the dialysis procedure and slowly rebounds after the treatment. Therefore, it is critical that the measurement be done pre-dialysis after a three-day interdialytic interval to obtain the most accurate value. If strict guidelines for use of L-carnitine are adhered to (i.e., the patient has true EPO-resistant anemia unexplained by any identifiable factor and true unexplained hypotension), then the use of L-carnitine in ESRD patients should be very uncommon. In conclusion, the clinical value of L-carnitine supplementation in hemodialysis patients remains to be documented by credible evidence from rigorous scientific studies. While "proof beyond a reasonable doubt" need not always be the requirement for reimbursement from payers, at a minimum "a preponderance of the evidence" should be documented in the literature. L-carnitine may prove to be a beneficial supplement. However, before justifying a national coverage policy, a new randomized, prospective controlled trial should be conducted to determine the utility of i.v. L-carnitine supplementation for anemia management and refractory dialysis-associated hypotension. Cost-benefit analysis is a critical aspect of such a study because it is important to determine the total cost (no matter who pays) of L-carnitine supplementation as compared to money saved by a reduction in EPO and iron administration. When reimbursement policies are developed, they need to be rational and based on the best evidence that is available. An NKF Carnitine Consensus Conference concluded that current literature and clinical experience leave unanswered questions regarding the use of L-carnitine in dialysis patients. Until there is scientific evidence to support use of L-carnitine supplementation, and it proves to be cost-effective, reimbursement is not justified. Therefore, the current CMS reimbursement decision for L-carnitine appears to be flawed.

Glomerular therapeutics: looking back, looking forward

Fifty years ago, the prospects for treatment of glomerulonephritis were dim. Beginning around 1950 the field of "glomerular therapeutics" was begun by the introduction of new agents (adrenocorticotrophic hormone, cortisone, nitrogen mustard) as possible disease-modifying therapies for the various forms of glomerular disease. For the next several decades these and other agents (azathioprine, cyclophosphamide, chlorambucil, prednisone) were used therapeutically in a largely uncontrolled and anecdotal fashion. The application of randomized, controlled trials led to the adoption of some forms of therapy as both effective and reasonably safe, and the rejection of others as either ineffective or hazardous. New regimens involving different routes of administration or dosing schedules were adopted. After about another two decades, new and increasingly selective agents began to be introduced into the therapeutic armamentarium (cyclosporine, mycophenolate mofetil). Diseases previously associated with a very poor outcome were transformed into manageable disorders. The consequences of glomerular disease (e.g., nephrotic syndrome, chronic renal failure) were now subject to control and alleviation in many circumstances. The next transformation of "glomerular therapeutics" is now under way. The revolution in molecular genetics and pharmacogenomics will allow new agents to be developed that target specific aspects of the pathogenic mechanisms underlying glomerular disease. This transformation will not be an easy one, because development, testing, approval, and application of these new concepts in therapeutics (e.g., somatic gene therapy) will be time consuming and expensive. Eventually, the understanding of the genetic basis of susceptibility to glomerular disease and its progression will allow a preventative and curative, rather than palliative, strategy to emerge.