Has the time now come to more widely accept hemodiafiltration in the United States?

Global real-world data on hemodiafiltration: An opportunity to complement clinical trial evidence

Hemodiafiltration (HDF) is a renal replacement therapy that utilizes both diffusive clearance and convective transport to achieve greater clearance of middle-molecular-weight solutes. Among other factors, important prerequisites for the implementation of HDF include access to high-flux dialyzers, achievement of high blood flow rates, and availability of high volumes of sterile substitution/replacement fluids. Online hemodiafiltration (OL-HDF) is an established kidney replacement therapy, frequently used in many countries. Although in the United States, some prerequisites (e.g., access to high-flux dialyzers and achievement of high blood flow rates) for OL-HDF treatment are readily available; however, a machine capable of generating the online solution for OL-HDF is currently not available. As the clinical experience with HDF accumulates globally, it is worth examining the evidence for this kidney replacement therapy as used in routine clinical care. Such real-world evidence is increasingly recognized as valuable by clinicians and may inform regulatory decisions. In this review, we will focus on emerging global real-world data derived from routine clinical practices and examine how these data may complement those derived from clinical trials.

The real-world effectiveness of sucroferric oxyhydroxide in European hemodialysis patients: a 1-year retrospective database analysis

BACKGROUND

The iron-based phosphate binder (PB), sucroferric oxyhydroxide (SFOH), demonstrated its effectiveness for lowering serum phosphate levels, with low daily pill burden, in clinical trials of dialysis patients with hyperphosphatemia. This retrospective database analysis evaluated the real-world effectiveness of SFOH for controlling serum phosphate in European hemodialysis patients.

METHODS

De-identified patient data were extracted from a clinical database (EuCliD®) for adult hemodialysis patients from France, Italy, Portugal, Russia and Spain who were newly prescribed SFOH for up to 1 year as part of routine clinical care. Serum phosphate and pill burden were compared between baseline (3-month period before starting SFOH) and four consecutive quarterly periods of SFOH therapy (Q1-Q4; 12 months) in the overall cohort and three subgroups: PB-naïve patients treated with SFOH monotherapy (mSFOH), and PB-pretreated patients who were either switched to SFOH monotherapy (PB → mSFOH), or received SFOH in addition to another PB (PB + SFOH).

RESULTS

1096 hemodialysis patients (mean age: 60.6 years; 65.8% male) were analyzed, including 796, 188 and 53 patients in, respectively, the PB + SFOH, mSFOH, and PB → mSFOH groups. In the overall cohort, serum phosphate decreased significantly from 1.88 mmol/L at baseline to 1.77-1.69 mmol/L during Q1-Q4, and the proportion of patients achieving serum phosphate ≤1.78 mmol/L increased from 41.3% at baseline to 56.2-62.7% during SFOH treatment. Mean PB pill burden decreased from 6.3 pills/day at baseline to 5.0-5.3 pills/day during Q1-Q4. The subgroup analysis found the proportion of patients achieving serum phosphate ≤1.78 mmol/L increased significantly from baseline during SFOH treatment in the PB + SFOH group (from 38.1% up to 60.9% [Q2]) and the mSFOH group (from 49.5% up to 75.2% [Q2]), but there were no significant changes in the PB → mSFOH group. For the PB + SFOH group, serum phosphate reductions were achieved with a similar number of PB pills prescribed at baseline prior to SFOH treatment (6.5 vs 6.2 pills/day at Q4). SFOH daily pill burden was low across all 3 subgroups (2.1-2.8 pills/day).

CONCLUSION

In this real-world study of European hemodialysis patients, prescription of SFOH as monotherapy to PB-naïve patients, or in addition to existing PB therapy, was associated with significant improvements in serum phosphate control and a low daily pill burden.

Enhancement of solute clearance using pulsatile push-pull dialysate flow for the Quanta SC+: A novel clinic-to-home haemodialysis system

BACKGROUND AND OBJECTIVE

The SC+ haemodialysis system developed by Quanta Dialysis Technologies is a small, easy-to-use dialysis system designed to improve patient access to self-care and home haemodialysis. A prototype variant of the standard SC+ device with a modified fluidic management system generating a pulsatile push-pull dialysate flow through the dialyser during use has been developed for evaluation. It was hypothesized that, as a consequence of the pulsatile push-pull flow through the dialyser, the boundary layers at the membrane surface would be disrupted, thereby enhancing solute transport across the membrane, modifying protein fouling and maintaining the surface area available for mass and fluid transport throughout the whole treatment, leading to solute transport (clearance) enhancement compared to normal haemodialysis (HD) operation.

METHODS

The pumping action of the SC+ system was modified by altering the sequence and timings of the valves and pumps associated with the flow balancing chambers that push and pull dialysis fluid to and from the dialyser. Using this unique prototype device, solute clearance performance was assessed across a range of molecular weights in two related series of laboratory bench studies. The first measured dialysis fluid moving across the dialyser membrane using ultrasonic flowmeters to establish the validity of the approach; solute clearance was subsequently measured using fluorescently tagged dextran molecules as surrogates for uraemic toxins. The second study used human blood doped with uraemic toxins collected from the spent dialysate of dialysis patients to quantify solute transport. In both, the performance of the SC+ prototype was assessed alongside reference devices operating in HD and pre-dilution haemodiafiltration (HDF) modes.

RESULTS

Initial testing with fluorescein-tagged dextran molecules (0.3 kDa, 4 kDa, 10 kDa and 20 kDa) established the validity of the experimental pulsatile push-pull operation in the SC+ system to enhance clearance and demonstrated a 10 to 15% improvement above the current HD mode used in clinic today. The magnitude of the observed enhancement compared favourably with that achieved using pre-dilution HDF with a substitution fluid flow rate of 60 mL/min (equivalent to a substitution volume of 14.4 L in a 4-hour session) with the same dialyser and marker molecules. Additional testing using human blood indicated a comparable performance to pre-dilution HDF; however, in contrast with HDF, which demonstrated a gradual decrease in solute removal, the clearance values using the pulsatile push-pull method on the SC+ system were maintained over the entire duration of treatment. Overall albumin losses were not different.

CONCLUSIONS

Results obtained using an experimental pulsatile push-pull dialysis flow configuration with an aqueous blood analogue and human blood ex vivo demonstrate an enhancement of solute transport across the dialyser membrane. The level of enhancement makes this approach comparable with that achieved using pre-dilution HDF with a substitution fluid flow rate of 60 mL/min (equivalent to a substitution volume of 14.4 L in a 4-hour session). The observed enhancement of solute transport is attributed to the disruption of the boundary layers at the fluid-membrane interface which, when used with blood, minimizes protein fouling and maintains the surface area.

Clinical evidence on haemodiafiltration

Haemodiafiltration (HDF) combines diffusive and convective solute removal in a single treatment session. HDF provides a greater removal of higher molecular weight uraemic retention solutes than conventional high-flux haemodialysis (HD). Recently completed randomized clinical trials suggest better patient survival with online HDF. The treatment is mainly used in Europe and Japan. This review gives a brief overview of the presently available evidence of the effects of HDF on clinical end points, it speculates on possible mechanisms of a beneficial effect of HDF as compared with standard HD and ends with some perspectives for the future.

Mortality risk in patients on hemodiafiltration versus hemodialysis: a 'real-world' comparison from the DOPPS

Background

With its convective component, hemodiafiltration (HDF) provides better middle molecule clearance compared with hemodialysis (HD) and is postulated to improve survival. A previous analysis of Dialysis Outcomes and Practice Patterns Study (DOPPS) data in 1998-2001 found lower mortality rates for high replacement fluid volume HDF versus HD. Randomized controlled trials have not shown uniform survival advantage for HDF; in secondary (non-randomized) analyses, better outcomes were observed in patients receiving the highest convection volumes.

Methods

In a 'real-world' setting, we analyzed patients on dialysis >90 days from seven European countries in DOPPS Phases 4 and 5 (2009-15). Adjusted Cox regression was used to study HDF (versus HD) and mortality, overall and by replacement fluid volume.

Results

Among 8567 eligible patients, 2012 (23%) were on HDF, ranging from 42% in Sweden to 12% in Germany. Median follow-up was 1.5 years during which 1988 patients died. The adjusted mortality hazard ratio (95% confidence interval) was 1.14 (1.00-1.29) for any HDF versus HD and 1.08 (0.92-1.28) for HDF >20 L replacement fluid volume versus HD. Similar results were found for cardiovascular and infection-related mortality. In an additional analysis aiming to avoid treatment-by-indication bias, we did not observe lower mortality rates in facilities using more HDF (versus HD).

Conclusions

Our results do not support the notion that HDF provides superior patient survival. Further trials designed to test the effect of high-volume HDF (versus lower volume HDF versus HD) on clinical outcomes are needed to adequately inform clinical practices.

Haemodiafiltration and mortality in end-stage kidney disease patients: a pooled individual participant data analysis from four randomized controlled trials

BACKGROUND

Mortality rates remain high for haemodialysis (HD) patients and simply increasing the HD dose to remove more small solutes does not improve survival. Online haemodiafiltration (HDF) provides additional clearance of larger toxins compared with standard HD. Randomized controlled trials (RCTs) comparing HDF with conventional HD on all-cause and cause-specific mortality in end-stage kidney disease (ESKD) patients reported inconsistent results and were at high risk of bias. We conducted a pooled individual participant data analysis of RCTs to provide the most reliable evidence to date on the effects of HDF on mortality outcomes in ESKD patients.

METHODS

Individual participant data were used from four trials that compared online HDF with HD and were designed to examine the effects of HDF on mortality endpoints. Bias by informative censoring of patients was resolved. Hazard ratios (HRs) and 95% confidence intervals (95% CI) comparing the effect of online HDF versus HD on all-cause and cause-specific mortality were calculated using the Cox proportional hazard regression models. The relationship between convection volume and the study outcomes was examined by delivered convection volume standardized to body surface area.

RESULTS

After a median follow-up of 2.5 years (Q1-Q3: 1.9-3.0), 769 of the 2793 participants had died (292 cardiovascular deaths). Online HDF reduced the risk of all-cause mortality by 14% (95% CI: 1%; 25%) and cardiovascular mortality by 23% (95% CI: 3%; 39%). There was no evidence for a differential effect in subgroups. The largest survival benefit was for patients receiving the highest delivered convection volume [>23 L per 1.73 m(2) body surface area (BSA) per session], with a multivariable-adjusted HR of 0.78 (95% CI: 0.62; 0.98) for all-cause mortality and 0.69 (95% CI: 0.47; 1.00) for cardiovascular disease mortality.

CONCLUSIONS

This pooled individual participant analysis on the effects of online HDF compared with conventional HD indicates that online HDF reduces the risk of mortality in ESKD patients. This effect holds across a variety of important clinical subgroups of patients and is most pronounced for those receiving a higher convection volume normalized to BSA.

A patient-centered vision of care for ESRD: dialysis as a bridging treatment or as a final destination?

The ESRD population is heterogeneous, including patients without severe comorbidity for whom dialysis is a bridge to transplantation or a long-term maintenance treatment, as well as patients with a limited life expectancy as a result of advanced age or severe comorbidity for whom dialysis will be the final treatment destination. The complex medical and social context of this latter group fits poorly in the homogeneous, disease-centered, and process-driven approach of many clinical practice guidelines for dialysis. In this commentary, we argue that the standards of treatment allocated to each individual patient should be defined not merely by his or her disease state, but also by his or her preferences and prognosis. In this more patient-centered approach, three attainable treatment goals with a corresponding therapeutic approach could be defined: (1) dialysis as bridging or long-term maintenance treatment, (2) dialysis as final treatment destination, and (3) active medical management without dialysis. For patients with a better overall prognosis, this approach will emphasize complication prevention and long-term survival. For patients with a limited overall prognosis, strictly disease-centered interventions often impose a treatment burden that does not translate into a proportional improvement in quantity or quality of life. For these patients, a patient-centered approach will place more emphasis on palliative management strategies that are less disease specific.

High-efficiency on-line haemodiafiltration improves conduit artery endothelial function compared with high-flux haemodialysis in end-stage renal disease patients

BACKGROUND

Middle molecular weight uraemic toxins are considered to play an important role in vascular dysfunction and cardiovascular outcomes in end-stage renal disease (ESRD) patients. Recent dialysis techniques based on convection, specifically high-efficiency on-line haemodiafiltration (HDF), enhance the removal of middle molecular weight toxins and reduce all-cause mortality in haemodialysis (HD) patients. However, the mechanisms of these improved outcomes remain to be established.

METHODS

This prospective study randomly assigned 42 ESRD patients to switch from high-flux HD to high-efficiency on-line HDF (n=22) or to continue HD (n=20). Brachial artery endothelium-dependent flow-mediated dilatation, central pulse pressure, carotid artery intima-media thickness (IMT), internal diastolic diameter and distensibility and circulating markers of uraemia, inflammation and oxidative stress were blindly assessed before and after a 4-month follow-up.

RESULTS

Brachial flow-mediated dilatation and carotid artery distensibility increased significantly in the HDF group compared with HD, while carotid IMT and diameter remained similar. HDF decreased predialysis levels of the uraemic toxins β2-microglobulin, phosphate and blood TNFα mRNA expression. Oxidative stress markers were not different between the HD and HDF groups. Blood mRNA expression of protein kinase C β2, an endothelial NO-synthase (eNOS) inhibitor, decreased significantly with HDF.

CONCLUSIONS

High-efficiency on-line HDF prevents the endothelial dysfunction and stiffening of the conduit arteries in ESRD patients compared with high-flux HD. HDF decreases uraemic toxins, vascular inflammation, and is associated with subsequent improvement in eNOS functionality. These results suggest that reduced endothelial dysfunction may be an intermediate mechanism explaining the beneficial outcomes associated with HDF.