High-volume hemodiafiltration emerges as new standard for dialysis

For patients with chronic kidney disease, dialysis is a lifelong treatment. However, patient survival rates have shown little significant improvement over the decades. High-volume hemodiafiltration (HVHDF) emerged as a treatment to overcome this limitation. Recent clinical studies confirm that HVHDF reduces the risk of death by 23 percent compared to conventional hemodialysis (HD) and also improves patients' quality of life (QoL), drawing attention as a new standard of treatment.

However, HVHDF inevitably incurs a certain level of additional costs related to equipment, consumables, and electricity and water usage. University hospitals can manage these costs, but general medical institutions are structurally hesitant to adopt it due to limitations in the fee-for-service system. Professor Jo Young-il of the Department of Nephrology at Konkuk University Medical Center, who chairs the Hemodialysis and Filtration Research Committee of the Korean Society of Nephrology, emphasizes that since the clinical efficacy of HVHDF is clear, a system supporting increased patient access is now needed.

Question: What are the concepts behind HD, HDF, and HVHDF?

Answer: HD uses the ‘diffusion’ principle to remove small-molecule uremic toxins. HDF (hemodiafiltration) adds “convection” to this, enabling the removal of medium-molecule toxins as well. While the kidney filters both large and small molecules, HD was limited to small molecules. HDF addresses this limitation.

HVHDF is a treatment that ensures sufficient “convective volume.” Multiple studies have clearly demonstrated improved survival rates when using at least 23 liters of replacement fluid. The CONVINCE study also demonstrated that it reduced the risk of death by approximately 23 percent compared to HD. The treatment efficacy is determined not simply by “whether it is HDF or not,” but by “how much sufficient convective volume was provided.”

Q: What is the clinical significance of the CONVINCE study? How did this study prove that HVHDF is an effective treatment for patients?

A: The CONVINCE study, published in the New England Journal of Medicine in 2023, was designed to address the limitations of previous studies. While data from countries like Japan and New Zealand also showed HDF improved survival rates, these studies had limitations that CONVINCE aimed to resolve.

In 2021, Korea's clinical guidelines still stated that “HDF cannot be recommended as standard treatment and may change based on randomized clinical trial results.” Therefore, there were high expectations for the CONVINCE study results, which were anticipated to resolve the controversy surrounding the clinical efficacy of HDF.

The CONVINCE study was designed as a large-scale randomized controlled trial involving approximately 1,360 patients across 61 centers in eight European countries, addressing the limitations of the smaller ESHOL study. The results confirmed a statistically significant reduction in mortality risk of approximately 23 percent with HVHDF compared to HD.

The study concluded there is no longer room for debate on the clinical utility of HVHDF. Therefore, if the hospital has the necessary conditions, HVHDF must be implemented.

Subsequently, the CONVINCE PRO study was conducted using the same patient population as the CONVINCE study. The primary endpoint of the CONVINCE study, overall mortality, showed a significant improvement. However, what patients actually experience is less about extended survival and more about feelings like “I feel uncomfortable after dialysis today” or “I feel refreshed after this dialysis session.” This is precisely what Quality of Life (QoL) is about.

Analysis of the CONVINCE PRO study confirmed that HVHDF, compared to HD, showed improvement effects across various QoL indicators, including physical function, cognitive function, pain interference, and social activities. Some results even showed improvements in mental health. This demonstrates that HVHDF is a treatment that not only improves survival time but also enhances quality of life.

Q: What changes does HVHDF bring to patients' lives?

A: Many patients stand out in my memory. One young man had a darkened complexion because HD alone couldn't sufficiently remove uremic toxins, but after switching to HVHDF, his complexion visibly improved. Another patient suffered from restless legs syndrome, but after HVHDF, the symptoms disappeared completely—to the point where he protested, “Why didn't I get this treatment sooner?”

Of course, these changes do not occur identically in every patient. Some patients do not see improvement in their RLS. However, there are several cases where problems unresolved by conventional HD are improved through HVHDF. Moreover, from the patient's perspective, HD and HVHDF feel almost identical, causing no discomfort, so there is no reason to avoid it. From the physician's perspective, we have no choice but to actively recommend HVHDF.

Q: So, is switching all patients to HVHDF the right direction?

A: In conclusion, yes. Sufficient evidence has now accumulated demonstrating HVHDF's superiority over HD. However, several practical barriers exist for actual implementation, including equipment and water purification facilities, a lack of operational experience, and, most critically, the ‘cost’ issue.

HVHDF consumes more water and electricity than HD, and in some cases, filter replacement costs or blood circuit costs also arise. Large university hospitals can manage this, but at smaller clinics, where fees are fixed, implementing HVHDF could actually result in losses.

Q: For HVHDF to be widely adopted in clinical practice, improvements to the reimbursement fee structure appear necessary. How specifically do you think the fee system should be adjusted?

A: Currently, dialysis fees in Korea are identical for HD and HVHDF. This means that even though more resources are invested, the compensation is the same. In Japan, when the HVHDF fee was slightly increased above the HD fee in 2012, the implementation rate surged dramatically from 10 percent to 47 percent. Europe also has an HVHDF implementation rate exceeding 50 percent. In contrast, Korea's rate is still only 10 percent.

Changing insurance policies would alter this situation. For example, if differential fees were applied—say, 135,000 won ($97) for HD and 140,000 won for HVHDF—hospitals would readily choose HVHDF. This is the most practical and effective way to improve patient access.

Q: What efforts are needed in the clinical field to spread HVHDF?

A: First is improving awareness of its safety. In the past, concerns about solution contamination or blood flow rate issues hindered adoption; however, with advances in purification technology, no safety issues have been reported. Second is education and sharing experience. Nurses and doctors may feel burdened initially, but within two to three weeks, they can operate it just as easily as they would with HD. Lastly, institutional support is crucial. Hospitals with existing facilities and equipment can implement it immediately, but without adequate reimbursement support, the pace of adoption will inevitably be slow.

Q: What would you emphasize for the rapid adoption of HVHDF, and what message would you like to convey to primary care providers?

A: For centers that already have the facilities and equipment for HVHDF but haven't implemented it due to various factors, they can start right away. In practice, it is safe and not difficult. Above all, the satisfaction of providing patients with the best possible treatment is immense.

I believe institutional backing, such as insurance reimbursement policies, is the way to further encourage this. Examining experiences in Europe, or specifically Japan, once such systems are in place, adoption will undoubtedly increase significantly.

However, there is a significant difference between university hospitals and private hospitals. Konkuk University Medical Center has studied and prepared facilities for nearly 20 years, accumulating experience that makes implementation possible. However, private hospitals may not be in the same position.

While uniform implementation may be difficult, it is desirable for hospitals already equipped with the necessary devices and facilities to implement it. This is because, even if better treatments known to date may emerge in the future, it allows for providing the optimal treatment until then.