Therapeutic apheresis (TFA) is the treatment of choice for various pathologies; the relevant indications and guidelines are outlined in the Guidelines on the Use of Therapeutic Apheresis in Clinical Practice (ASFA).1 Given that nephrologists are well-trained in TFA, many nephrology services have incorporated the different modalities of this technique into their service portfolios and have applied it to both renal and extrarenal pathologies. In recent years, AFT-based chronic treatment programs have been implemented in a growing number of centers.

In 2013, the Working Group of Therapeutic Apheresis of the Spanish Society of Nephrology (Aféresis Terapéutica de la Sociedad Española de Nefrología, AFT-SEN) administered a nationwide survey to identify which nephrology services offered AFT in Spain, and 30 services responded.2 That same year, the project to create an apheresis registry was proposed at the XLII Congress of the SEN. In 2018, a new survey on the offering of AFT services was administered, to which 60 services responded, 12 of which reported that they had developed chronic treatment programs in the previous five years. Several centers confirmed the incorporation of new modalities of TFA, such as rheoapheresis, photopheresis, and low-density lipoprotein (LDL) apheresis, among others. The results were presented at the 48th Congress of the SEN, after which the National AFT Registry was implemented.3

Initial data from the AFT-SEN registry were presented at the 50th Congress of the SEN in 2020.3 The main objectives of registry,4 as summarized in Table 1, were to record the number of patients treated in different nephrology departments, the AFT techniques implemented, the clinical protocols used, and the safety variables evaluated—all of which are needed to optimize clinical practice. To our knowledge, there are no published records of TFA use in nephrology services, and therefore no direct comparisons can be made. There are, however, data from international hematology registries as well as from the World Apheresis Association (WAA),5 which resulted from the 2002 merger of the Canadian, French and Swedish registries and the participation of Spanish hematology services.6–8 Currently, this latter registry has information from more than 140,000 patients from 19 countries.9 As these data come from hematology and blood bank services, they involve different indications and modalities of TFA, limiting comparative extrapolation with our registry.

The objective of the present work is to describe the use of AFT in the nephrology services participating in the AFT-SEN registry.

This descriptive observational study included all TFA procedures registered consecutively in the Therapeutic Apheresis Registry of the SEN between 2019 and 2023. Nineteen nephrology departments reported a total of 4331 procedures for 525 patients. Of the 19 nephrology departments, 17 (89.5%) are publicly owned centers, and 2 (10.5%) are privately owned. Furthermore, of the 19 nephrology centers, 18 are classified as adult nephrology centers, and one is a pediatric nephrology center.

The data are presented as absolute numbers, percentages, medians and interquartile ranges (IQRs). Descriptive analysis was performed with the statistical package SPSS V.21 (Chicago, IL).

The data from the AFT-SEN registry represents the first records of TFA use in the field of nephrology in Spain and reflect the widespread use of apheresis techniques by nephrologists. The number of participating centers has increased significantly, from seven in 2018–2020 to 19 in 2023.2,3 Compared with the results presented in 2020, the results of this study revealed the progressive incorporation of new modalities of AFT beyond PE, including specific and nonspecific immunoadsorption, double filtration, leukocytapheresis and photopheresis. Similarly, new plasma separation techniques, such as centrifugation, have been introduced, and the forms of vascular access has expanded, with the aim of optimizing both the efficacy and safety of the procedure. The availability of these technologies has allowed the diversification of nephrology services and the extension of TFA to nonrenal patients. In fact, between 2018 and 2020, neurological patients constituted the most frequently treated group—more numerous than renal patients—with multiple sclerosis being the most common neurological indication.2,3 These results coincide with the data published by the WAA, in which neurological patients are the most commonly treated after hematological patients, particularly patients with myasthenia gravis.4,6,8 The needs derived from the management of nonrenal patients have aided in the creation of chronic treatment programs in nine nephrology services, three more than those registered in 2018.

It should be noted that, according to the ASFA guidelines, all the indications included in the registry could be classified as category I, II, or III, while none could be classified as category IV, indirectly suggesting the implementation of good clinical practices.1 The safety analysis revealed a low incidence of adverse effects; hypotension appeared mainly in filtration-based PE procedures, while it has not been described in centrifugation-based PE. Mechanical complications, on the other hand, are recorded for both techniques and are mainly related to vascular access problems. Since the incidence of adverse effects depends on the technique, the type of vascular access, and the replacement fluid used, there is notable variability across centers, which limits the possibility of drawing more general conclusions. Together, these results reveal the progressive integration of TFA in nephrology clinical practice despite differences in its methodology across centers. While some centers are limited to only PE for renal patients, others have developed a broader portfolio of techniques and chronic treatment programs, thus expanding the scope of TFA to extrarenal pathologies.5,6,8

A relevant observation from the data presented is the difficulty in establishing consistent comparisons with other series, both national and international. Unlike in hematology centers, where there is a longer tradition of multicenter cooperation in completing the records, in nephrology centers, data are often fragmented and heterogeneous, which limits extrapolation and precludes robust comparative analyses. The lack of standardized practices across centers similarly raises issues regarding interpretations of results and the evaluation of safety, particularly if differences in the techniques used and differences in vascular accesses are considered.

These findings reinforce the need to increase participation in the AFT-SEN Registry as a national standardization strategy to harmonize the collection of clinical, technical, and safety variables and to advance equity in access to all therapeutic apheresis techniques.

The use of international registries, such as the WAA Registry—the result of the merger of Canadian, French and Swedish registries—has led to the development of a common framework that can subsequently be used to improve the quality of care and facilitate research.2–4,9,10 Increasing participation in the AFT-SEN Registry would allow not only comparisons across centers but also the identification of areas of improvement, the design of multicenter studies and the development of specific clinical guidelines in nephrology. Similarly, it could improve the visibility of the discipline among specialty services, reinforce the role of nephrology in collaboration with other disciplines, and improve access to therapeutic apheresis at the national level.

Finally, it is essential to advance the development of common clinical protocols, promote multicenter studies and encourage the publication of results that consolidate and provide visibility to the growing role of TFA in nephrology services.

This study has several limitations that should be considered. First, the voluntary participation of only 19 nephrology services may not fully reflect the use of TFA at the national level, as potential selection bias and underreporting may affect the results. The observational and descriptive design of the registry prevents the establishment of causal associations and the assessment of the comparative efficacy of the different techniques. Similarly, differences in the indications for TFA and the profiles of patients treated as well as differences in the resources available to the centers warrant careful interpretation of the results.

We declare that this research has not received support from public sector agencies, the commercial sector or nonprofit entities.