Work status and work ability of patients receiving kidney replacement therapy: results from a European survey

ABSTRACT

Background

Employment is important for the quality of life and financial security of patients of working age receiving kidney replacement therapy (KRT). We aimed to examine self-reported work status and general, physical and mental work ability and to determine associations between demographic, disease-related, work-related and macroeconomic factors and employment. 

Methods

Europeans from 37 countries, ages 19–65 years, treated with dialysis or kidney transplantation, filled out the web-based or paper-based cross-sectional EDITH kidney patient survey between November 2017 and January 2019. We performed descriptive analyses and multivariable generalized logistic mixed models.

Results

Of the 3544 patients, 36.5% were employed and working [25.8% of dialysis patients, 53.9% of kidney transplant recipients (KTRs)]. The mean general work ability was 5.5 out of 10 (dialysis: 4.8, KTRs: 6.5). Non-working patients (all: 4.1, dialysis: 3.9, KTRs: 4.7) scored lower than working patients (all: 7.7, dialysis 7.3, KTRs: 8.0). Working dialysis patients scored lower on physical and mental work ability (7.1 and 8.1) than working KTRs (8.0 and 8.4; P < 0.001). Impaired physical work ability (42.7%) was more prevalent than impaired mental work ability (26.7%). Male sex, age 40–49 years, higher education, home dialysis or kidney transplantation as current treatment, treatment history including kidney transplantation, absence of diabetes mellitus, better general work ability and higher country gross domestic product were positively associated with employment (P < 0.05).

Conclusions

Low employment rates and impaired work ability were prevalent among European patients receiving KRT. Demographic, disease-related, work-related and macro-economic factors were associated with employment.

INTRODUCTION

In Europe, ≈330 000 individuals of working age suffer from end-stage kidney disease (ESKD) and receive kidney replacement therapy (KRT) [1]. Patients receiving KRT find it important to be able to work, as it provides an income, social contact and the ability to contribute to society [2–5].

‘Work status' refers to involvement in paid work while ‘work ability’ involves assessment of whether one is currently sufficiently capable to perform work given one's health condition [6, 7]. Several single-country studies have reported on work status and work ability in patients receiving KRT [8–18]. However, these studies are difficult to compare, as work status and/or work ability were defined and measured in different ways, study populations were heterogeneous and social security systems differed markedly between countries. Furthermore, none have previously distinguished between physical and mental work ability, while this information is relevant for interventions to support employment. Moreover, several studies have addressed work status and work ability in kidney transplant recipients (KTRs) [10, 11, 17], whereas the few studies in dialysis patients are dated and suffer from small sample sizes [12–14]. Notably, one-third of KRT patients of working age are receiving dialysis [1].

To date, several studies have described factors (e.g. demographic, disease-related, work-related) related to job prospects of patients receiving KRT [8, 10, 11, 15–18]. However, the impact of macroeconomic factors such as country gross domestic product (GDP) on employment has not yet been studied. GDP is an indicator of a country's wealth and may influence treatment modality choice on the country level [19], which in turn may affect job prospects of KRT patients. In addition, country wealth may influence the availability of jobs, the employers’ willingness to hire persons with chronic diseases and the quality of social security systems.

Currently a comprehensive European study using uniform measures for work status and work ability in patients receiving KRT is lacking. Therefore the aims of this study were to examine self-reported work status and work ability and determine associations between demographic, disease-related, work-related and macroeconomic factors and employment in European ESKD patients of working age treated with dialysis or kidney transplantation (KTx).

MATERIALS AND METHODS

Participants

We used data from the EDITH kidney patient survey [20]. European adults with ESKD treated by any form of dialysis or KTx could participate. The current dataset included respondents ≤65 years of age who had started KRT at or older than the age of 18 years, whereas retirees (n = 829), those with missing work status (n = 25) or those living outside Europe were excluded (n = 177).

Ethical aspects

The Medical Ethics Committee of the Amsterdam University Medical Centers, location AMC, judged that a comprehensive evaluation was not required since this study was not subject to the Dutch Medical Research Involving Human Subjects Act (W17 291#17.343). If deemed necessary by local hospitals, nephrologists obtained approval from their local ethics committee. Participation was voluntary.

Survey development and translation

For a complete overview of the survey's development and translation, we refer to the original article about the EDITH kidney patient survey [20]. Briefly, we designed the survey using existing literature, input from a kidney patients’ advocate and questions about work ability from validated surveys. The survey was translated into 31 languages (Supplementary data, item 1) and offered on paper or web-based via LimeSurvey [21].

Data collection

The survey was promoted and distributed by local and national kidney patients’ associations, the European Kidney Patients’ Federation, the European Renal Association–European Dialysis and Transplantation Association, national societies of nephrology and individual nephrologists and their colleagues between November 2017 and January 2019.

We collected the following demographic variables: sex, year of birth, education level (no school/primary/secondary/vocational/higher education) and country. Countries were divided into tertiles based on 2016 gross domestic purchasing power parity (GDP PPP) data from the World Bank to study the association between a country's wealth and employment of its KRT patients [22]. Disease-related variables included current and previous KRT modalities, waitlist status, start year of KRT and self-reported comorbidity [diabetes mellitus (DM) and malignancy].

Work-related variables included current work status, work ability and work hours (Supplementary data, item 2). Work status was dichotomized; respondents who were employed and working were classified as working and all others (employed and on sick leave, unemployed, student, housewife/house husband or receiving a disability pension) were classified as non-working. Work ability was measured with questions based on the Work Ability Index (WAI) [6, 7]. The question about general work ability asks one to compare one’s current work ability against one's lifetime best work ability. The questions about physical and mental work ability ask working respondents about the ability to meet their job's physical and mental demands. General, physical and mental work ability were all scored between 0 and 10 and higher scores suggest better work ability. Numeric scores were also categorized; a score of 0–5 was categorized as poor, 6–7 as moderate, 8–9 as good and 10 as excellent [23]. We obtained several standard translations of the WAI items, but if unavailable, they were translated from English into other languages by native speakers (Supplementary data, Item 1).

Data analysis

Respondent characteristics were reported as means with standard deviations (SDs) and medians with interquartile ranges (IQRs) for continuous variables and as proportions for categorical variables. We compared characteristics between working and non-working respondents and performed separate analyses for dialysis patients and KTRs. We tested for differences using chi-squared tests for categorical variables, Mann–Whitney U tests for comparison of means and median test for comparison of medians.

We investigated associations between respondent characteristics (sex, age, education level, current treatment, treatment history, DM, malignancy, duration of KRT, general work ability, country GDP) and employment for complete cases using generalized logistic mixed models (SAS proc glimmix) with binary distribution and log linkage for the outcome (working versus non-working), providing relative risks with 95% confidence intervals (CIs) as effect measures. We calculated McFadden's pseudo-R² to assess the proportion of variance in the dependent variable that is predictable from the independent variable [24]. Values of 0.2 to 0.4 for R² represent an excellent fit [25]. A random intercept was added to the model to account for clustering of respondents within countries; however, because most models failed to converge, we present these as supplementary data. Two multivariable regression models were considered. The first was adjusted for possible a priori selected confounders based on the criteria for confounding [26]. The second model additionally controlled for self-reported general work ability as an a priori selected potential mediator, as this variable could explain (part of) the association between the determinants and employment. Moreover, treatment modality–specific associations were studied by including an interaction term between the determinant of interest and the current treatment modality (dialysis or KTx). We performed a sensitivity analysis with these two models, including only patients with good or excellent work ability. Furthermore, we performed a sensitivity analysis including retirees, which produced no relevant differences as compared with the main analyses. P-values < 0.05 were considered statistically significant. Statistical analyses were performed with SPSS Statistics 26.0 (IBM, Armonk, NY, USA) and SAS 9.4 (SAS Institute, Cary, NC, USA) [27, 28]. Data cannot be shared publicly due to the privacy of individual survey participants.

RESULTS

Respondent characteristics and work status

We included 3544 dialysis patients and KTRs from 37 European countries (Figure 1; Supplementary data, Table S1). Their mean age was 49.8 years, 50.7% were male, 52.4% received in-centre haemodialysis and the mean KRT duration was 9.4 years (Table 1). A total of 38.4% of respondents lived in a low-GDP tertile country, 30.3% in a middle-GDP tertile country and 31.3% in a high-GDP tertile country. Sex and age distribution matched fairly with those of prevalent patients from the same countries in the European Renal Association Registry [1], but patients from middle-GDP countries were underrepresented in our sample (Supplementary data, Table S2).

A third (36.5%) of all respondents were working (i.e. employed and working), while the remaining were unemployed, student, housewife/house husband, receiving a disability pension or employed and on sick leave. The employment rate increased with better work ability: 11.1% of the patients with poor work ability were working compared with 47.9% of patients with moderate work ability, 69.2% of patients with good work ability and 79.3% of patients with excellent work ability.

Working respondents were more likely to live with a functioning transplant (56.1% versus 27.6%; P < 0.001), suffered less often DM (14.0% versus 23.9%; P < 0.001) and malignancy (2.4% versus 4.2%; P < 0.05) and were less likely to live in a low-GDP country (25.5% versus 45.8%; P < 0.05). Figure 2 and Supplementary data, Table S3 display the work status of respondents from seven countries with at least 150 respondents.

Employment was reported by 25.8% of dialysis patients and 53.9% of KTRs (Table 1). Working dialysis patients more frequently used a home-based dialysis modality, were more often on the KTx waitlist and suffered less often from DM or malignancy than non-working dialysis patients (P < 0.05). Working KTRs were more likely to have received a pre-emptive KTx or a living donor KTx compared with their non-working counterparts (P < 0.05).

General work ability

The mean general work ability in the total group of respondents was 5.5 on a 0 to 10-point scale (Table 1). Non-working respondents scored lower (4.1) than working respondents (7.7; P < 0.001). Two-thirds of all respondents reported impaired (poor or moderate) work ability. Notably, 40.9% of the working respondents reported impaired work ability, while 14.2% of the non-working respondents reported good or excellent work ability.

The mean work ability of dialysis patients was 4.8 (Table 1). Non-working dialysis patients scored lower (3.9) than working dialysis patients (7.3; P < 0.001). While half of the working dialysis patients were categorized as having good or excellent work ability, only one in eight non-working dialysis patients fell into this category (P < 0.001). Forty-nine percent of the working dialysis patients reported impaired work ability.

KTRs reported a mean work ability of 6.5 (Table 1) and this was lower in non-working patients (4.7) than in working patients (8.0; P < 0.001). While 65.5% of working KTRs reported good or excellent work ability, this was less frequently the case for non-working KTRs (18.4%; P < 0.001). Approximately one-third of the working KTRs reported impaired work ability.

Work hours, physical and mental work ability

Working patients receiving KRT reported an average of 33.8 work hours per week, with dialysis patients reporting fewer hours (31.6) than KTRs (35.4; P < 0.001) (Table 2). The mean physical work ability was lower (7.1) in dialysis patients compared with KTRs (8.0; P < 0.001). In total, 54.4% of dialysis patients and 33.3% of KTRs reported impaired physical work ability. The mean mental work ability was also lower in dialysis patients (8.1) than in KTRs (8.4; P < 0.001). Impaired mental work ability was reported by 30.6% of dialysis patients and 23.6% of KTRs.

Associations between respondents’ characteristics and employment

In unadjusted analyses, male sex, vocational/higher education, being treated with home dialysis or KTx (versus in-centre haemodialysis), history including KTx (versus only dialysis), being on KRT for more than 5 years, higher self-reported general work ability and living in a middle- or high-GDP country (versus low-GDP country) were positively associated with employment, whereas having DM or malignancy significantly reduced the likelihood of employment (Figure 3 and Supplementary data, Table S4). There was a non-linear association between age and employment, with the highest likelihood of being employed for patients ages 40–49 years. Malignancy was no longer significantly associated with employment when adjusting for sex and age (Supplementary data, Table S4). After adjustment for additional confounders, being on KRT for more than 5 years was no longer significantly associated with employment.

The addition of general work ability as a potential mediator to our models attenuated the effect of all associations (except for KRT duration). However, general work ability partially mediated the associations between age and employment in older (50–59 and 60–65 years) but not in younger patients (20–29 and 30–39 years).

Positive associations between vocational/higher education, current treatment with home dialysis or KTx, treatment history including KTx or higher country GDP and employment were also found in the subgroup of patients with good or excellent work ability (Supplementary data, Figure S1). Male sex was no longer significantly associated with employment in this subgroup.

Interaction analyses revealed that positive associations between vocational/higher education or country GDP and employment were stronger in dialysis patients compared with KTRs (P < 0.05) (Figure 4 and Supplementary data, Table S5). Similarly, negative associations between DM or being on KRT for more than 5 years and employment were stronger in dialysis patients (P < 0.05). Associations between the other variables (i.e. sex, age, malignancy and work ability) and employment were not significantly different for dialysis patients and KTRs.

The associations between higher education level or country GDP and employment were also stronger in dialysis patients compared with KTRs in the subgroup of patients with good or excellent work ability (Supplementary data, Figure S2). The association between DM or being on KRT for more than 5 years were not different between the two groups in this subgroup.

Analyses with country included as a random effect in the generalized logistic mixed models gave comparable results as models without random effects, except for GDP (Supplementary data, Table S6).

DISCUSSION

In this large multinational study, patients with ESKD receiving KRT from nearly all European countries were surveyed about their work status and work ability. We found a low employment percentage and impaired work ability among both dialysis patients and KTRs. Moreover, we identified several demographic, disease-related, work-related and macroeconomic factors associated with employment in these patients.

Work status

In our study, 36.5% of the patients receiving KRT were working. Only a quarter of the dialysis patients were employed and this low percentage could be explained by the poor health status of dialysis patients and the time required for dialysis treatments. KTRs usually have a better health status, but still only half of them were working, which is considerably less than the European average (73.2%) [29]. Our findings match the results found in several single-country studies in European KRT patients [8, 11, 14–17]. However, comparison between studies is hampered by differences in the classification of work status and heterogeneity of study populations.

Work ability

KTRs reported a mean general work ability of 8 out of 10, which is consistent with the literature [10, 17] and comparable with the average of European employees [30–35]. Working dialysis patients scored lower on average (7.3). However, one-third of working KTRs and half of the working dialysis patients reported impaired general work ability, whereas this applies to less than one-fifth of the European employees [31, 36–39]. Employees with other severe chronic diseases (e.g. DM, malignancy) have reported similar proportions of impaired general work ability [39, 40].

Interestingly, one in seven KRT patients rated their general work ability as good or excellent, even though they were not working. These patients may be willing to work but may experience discrimination in the job market. Furthermore, we hypothesize that sufficient unemployment or disability benefits may reduce the need to find a job in certain countries. On the other hand, in countries without disability benefits, patients may struggle to meet work demands in order to ensure an income.

This study was the first to distinguish between physical and mental work ability in KRT patients. Half of the working dialysis patients and one-third of working KTRs reported impaired physical work ability, whereas this is between 10 and 15% in the general population [41, 42]. Although impaired mental work ability was less frequently reported, the prevalence was still twice as high as that of the general population [41, 42].

Associations between respondents’ characteristics and employment

We found a positive association between male sex and employment, whereas others have provided conflicting evidence regarding this topic [8, 10, 11, 13, 14, 16, 17]. Our finding could potentially be explained by various sociological, legal and disease-related factors. First, traditional role patterns, in which men work outside the house while women invest time in the household and children, may play a role [11]. Lower employment percentages among European women of working age in the general population (67.4% versus 79.0% among men) support this assumption [29]. Moreover, some European countries have a lower retirement age for women than for men [43]. Second, the epidemiology and outcomes of chronic kidney disease (CKD) are different in men and women [44]. Female patients experience a worse quality of life, a higher symptom burden and more hospitalizations than men [44]. Furthermore, women are less often placed on the kidney transplant waitlist and more frequently have preformed antibodies that decrease their chance to receive a deceased donor kidney transplant [44, 45], although their access to living donor KTx does not seem to be limited [44, 45]. Pre-transplant employment, which is one of the most important predictors of employment after KTx [16, 46], was associated with male sex, which gives male patients a higher probability of employment [46].

We found a non-linear association between age and employment, with the highest likelihood of employment found in patients between 40 and 49 years old. Older patients were less likely to be employed [9, 16], but this also applied to the youngest patients in our study. The latter may have a history of CKD and other disabilities, causing them to reach developmental milestones later in life [47]. They may need more time to complete their education and may have limited work experience, leading to lower chances for employment [48].

In our multinational sample, we found a positive association between treatment with home dialysis or KTx and employment [8, 15]. Some suggest that KRT modality has no impact on employment, but rather, employment status influences the choice of KRT modality [14, 49]. Nephrologists and other healthcare professionals may be more likely to recommend home dialysis or KTx to working patients [50, 51].

A low education level and DM were both associated with lower employment rates in patients receiving KRT [8–11, 13, 15, 16]. For the first time, we investigated these associations within one study in dialysis patients and KTRs separately. We found a lower likelihood of employment in lower-educated or diabetic dialysis patients compared with KTRs. Dialysis patients usually have a worse physical condition, which may cause more difficulties in lower-educated patients who depend more on physically demanding jobs. Complications of DM, such as visual impairment, neuropathy and a higher incidence of cardiovascular events, may impede employment. The risk of complications may be different for dialysis patients and KTRs, as the latter may have new-onset DM after KTx, causing fewer complications due to a shorter disease duration and better glycaemic control [52].

Living in a middle- or high-GDP country, however, was associated with an increased likelihood of employment for dialysis patients but not for KTRs. Higher-income countries may experience an ageing workforce with shortages of employees, which could result in more opportunities in the labour market for persons with chronic diseases. Moreover, we speculate that higher-income countries have more possibilities for sick leave and part-time work, which can be beneficial for dialysis patients.

In line with previously published studies, the findings of our study show that work ability was strongly associated with employment not only in KTRs, but also in dialysis patients [10, 17]. Both groups could benefit from interventions to improve work ability [53, 54], which should ideally start before KRT initiation, as pretreatment work status is an important predictor of work status after KRT initiation [13, 15, 16]. Future studies may investigate the effect of treatment schedules (frequency and duration) on work status and work ability to offer optimal treatment to dialysis patients.

Strengths and limitations

This comprehensive survey included >3500 dialysis and kidney transplanted patients from 37 countries in Western and Eastern Europe. Work status and work ability were assessed using uniform questions in 31 different languages. However, our study has limitations. Regardless of the large sample size, only a fraction of all KRT patients living in the participating countries completed the survey. Due to this sampling bias, our findings may not be generalizable to all European patients receiving KRT. Previous single-country studies achieved full population coverage by linking data from the national bureau of statistics to data from renal registries to assess work status [8, 55]. This was impossible in our multinational study due to the absence of national renal registries, unavailability of data about work status on an individual patient level or the impossibility to link data. Moreover, one always relies on surveys to study work ability, which is subjective information. Selection bias is inherent to surveys and usually difficult to solve. Healthier and higher-educated patients who are more likely to be employed may be overrepresented in this study, which may have led to an overestimation of employment rate and work ability. We attempted to reduce selection bias by prior assessment of the survey's comprehensibility by patients, offering online and paper versions of the survey in 31 languages and assistance when filling out the survey. As patients were not directly approached by the research team, we were unable to calculate a response rate or compare respondents with non-respondents. Furthermore, work status was self-reported and some patients might have misinterpreted answer options. Although we were able to adjust for several confounders in the associations between respondents’ characteristics and employment, we were unable to control for other potentially relevant variables (e.g. work status before KRT initiation). For this reason, and due to the cross-sectional design of our study, we are unable to infer causality to our results.

CONCLUSION

We found that low employment rates and impaired work ability were highly prevalent in a large sample of European patients receiving KRT. Only a quarter of the European dialysis patients are working and a significant proportion of them struggle to meet the physical and mental demands of their job. Although KTRs generally have a better health status than dialysis patients, their employment rate and work ability also deserve attention, as they lag behind those in the general population.

Employment was associated with several patient characteristics, of which many are not modifiable. Treatment choice could be a modifiable characteristic. Patients may benefit from flexible dialysis shifts and improved access to home-based dialysis modalities and KTx, especially pre-emptive [16–18]. Furthermore, nephrologists and other healthcare professionals may discuss patients’ preferences about employment in an earlier stage of the disease, as early support may help employed patients to remain at work. As we found differences between lower- and higher-income countries in Europe, we believe that strategies to improve the work status of KRT patients should be tailored to socio-economic conditions.

ACKNOWLEDGEMENTS

The authors sincerely thank all patients who filled out the EDITH kidney patient survey. Moreover, we are grateful to all patients who pretested the survey, provided advice about the content of the survey or helped to distribute the survey in their country or personal network.

Among others, we are grateful for support from the following: Austria [ARGE Niere (D. Trinkl), Österreichische Transplantationsverband (M. Krimbacher), Verein Niere Vorarlberg (E. Längle)], Belgium [Fenier-Fabir and Nier Limburg (M. Mues)], Bosnia and Herzegovina [Udruženje Dializiranih & Transplantiranih Bolesnika Federacije BiH (T. Žuljević)], Bulgaria (Association of Patients with Kidney Diseases and Friends Bulgaria (H. Nikolova, R. Vaklinova)], Cyprus [Pancyprian Kidney Organization (E. Groutidou Petridou)], Denmark [Nyreforeningen (K. Ertmann Krammer, P. Holm Harmsen)], Finland [Munais- ja maksaliitto (S. Högström)], France [France REIN, Transforme (E. Lacour)], Greece [Greek Kidney Patients Federation (T. Papadopoulos, M. Sekadakis), Sports Federation For Dialysis & Transplant Athletes (D. Arka)], Hungary [Trapilap (J. Berente), Vesebetegek Egyesületeinek Országos Szövetsége (A. Ádám)], Ireland [Irish Kidney Association (M. Murphy, C. White)], Latvia [Latvijas Nieru Slimnieku Asociācijas (J. Baranovska-Kaša)], Lithuania (Gyvastis, Lietuvos Nefrologiniu Ligoniu Asociacija), Luxembourg [Dialyse Patienten Lëtzebuerg (L. Chrisnach)], Netherlands [Leef Nierpatiënten Vereniging Hilversum (P. Floor), NierNieuws, Nierpatiënten Vereniging Nederland (W. Konijn, K. Prantl), Nierpatiënten Vereniging Solidair (H. Zomer), Stichting Doneren en transplanteren (M. van der Gaag), Stichting Sport en Transplantatie (J. Folkers, F. Kuipers), Vereniging voor Nierpatiënten regio Den Haag (G. van der Pol)], North Macedonia [NEFRON Kidney Patient Association (P. Baliska, D. Gorgiev)], Norway [Landsforeningen for Nyrepasienter og Transplanterte (J. Anker Lisberg Sarpebakken, K. Fosser, M. Gonsholt, I. Østli, L. Skar)], Poland [Ogólnopolskie Stowarzyszenie Osób Dializowanych (M. Dębski-Korzec, A. Serwadczak)], Portugal [Associação Portuguesa de Insuficientes Renais (M. Campos)], Romania (Asociatia Transplantatilor din Romania (G. Tache, A. Teodorescu)], Slovenia [Sve Osmeh (J. Antic, B. Danilovic), Zveza Društev Ledvičnih Bolnikov Slovenije (L. Hajdinjak, B. Tome)], Spain [Federación Nacional de Asociaciones para la Lucha Contra las Enfermedades del Riñón (J. Carlos Julián Mauro, D. Gallego Azurro)], Sweden [Njürforbundet (H. Heddman, S. Norman, L. Pellborn), Ukraine (Nephro Nadiya) and from the following organizations: European Kidney Patients Federation (M. Murphy, C. White), South-east Europe transplant network Seentransplant (M. Osterc), PKD International (T. Harris) and NephCure (M. van Meel).

In addition, we wish to thank many international colleagues for their help. We are grateful to every person who has helped us by translating, promoting or distributing the EDITH kidney patient survey. Among others, we received support from Albania (A. Idrizi), Austria (R. Kramar, U. Lang, G. Mayer, R. Oberbauer, R. Reindl-Schwaighofer, S. Tabernig), Belarus (K. Komissarov, K. Kurylovich), Belgium (D. Abramowicz, F. Bonkain, M. Claes, S. Claus, F. Collart, J. De Meester, L. Heemeryck, E. Meersman, L. Moyson, C. Olbrechts, S. Verhofstede, C. Swyns, C. Tielemans, W. Van Biesen, R. Vanholder), Bosnia and Herzegovina (B. Čengić-Roljic, H. Resic), Bulgaria (E. Vazelov), Croatia (I. Bubić, M. Busic, M. Dragović, D. Lazarin, S. Živčić Ćosić), Cyprus (K. Ioannou, G. Marangou d'Avernas), Czech Republic (V. Borcany, I. Rychlik), Denmark (L. Boesby, J. Goya Heaf), Estonia (Ü. Pechter, M. Rosenberg—Ots), Finland (A. Cornér, P. Finne, R. Ikäheimo, R. Muroma-Karttunen), France [C. Couchoud, B. Hodemon Corne, V. Juventin, M. Laville, Z. Massy, M. Mongé, colleagues from Réseau épidémiologie et Information en Néphrologie (REIN)], Germany (M. Lingemann, A. Rahmel, F. Schaub, S. Venhaus), Greece (N. Afentakis, T. Apostolou, E. Dounousi), Hungary (O. Deme, A. Mezõ, G. Reúsz), Iceland (R. Pálsson, H. Runolfsdottir), Ireland (W. Plant), Italy (R. Benevento, V. Caramia, C. Carella, P. di Caccio, L. Gesualdo, E. Mancini, A. Meterangelis, A. Nanni Costa, M. Nordio, M. Postorino, V. Sparacino, C. Zocalli), Latvia (H. Cernevskis, L. Kucane, A. Petersons, A. Silda), Lithuania (I. Arūnė Bumblytė, V. Tilvikaitė, E. Žiginskienė), Luxembourg (M. Aurich, S. Azorin Contesse, C. Braun), Moldova (A. Tanase), Netherlands (J. Bijlsma, M. Boonstra, W. Bos, M. de Jong, G. Guggenheim-van der Hout, M. Hemmelder, A. Jaho, S. Kragten-Lathouwers, S. Logtenberg, I. van de Meerakker-Hegge, A. Neradova, M. van Oosten, A. Ozyilmaz, M. Pippias, D. Pitters, V. Sauve, D. Struijk), North Macedonia (G. Selim, O. Stojceva-Taneva), Norway (M. Andersen, A. Asberg, K. Lønning, A. Varberg Reisaeter), Poland (S. Dudzicz, G. Korejwo, M. Nowicki, A. Wieçek), Portugal (R. Aguiar, E. Almeida, S. Fernandes, F. Marcario), Romania (L. Garneata, G. Mircescu, G. Stefan, L. Tuta), Russia (A. Andrusev, E. Zakharova), Serbia (S. Bjelica, N. Maksimovic, R. Naumovic, M. Zaric), Slovakia (R. Roland, J. Rosenberger, V. Spustova), Slovenia (J. Buturovic Ponikvar, D. Kovac, M. Malgaj), Spain (P. Barreda, J. Cannata, M. Collado, M. del Pino y Pino, M. Enma Huarte Loza, A. Ortiz, H. Zambrana), Sweden (O. Bratt, M. Evans, H. Rydell, M. Stendahl), Switzerland (I. Françoise Binet, U. Huynh-Do, F. Immer, M. Weder, staff from Inselspital Universitätsspital Bern), Turkey (M. Arici, N. Seyahi), Ukraine (M. Kolesnyk, N. Stepanova, L. Surzkho) and Eurotransplant (P. Branger, M. van Meel, U. Samuel).

We would like to offer special acknowledgements to Prof. Judith K. Sluiter, who, although no longer with us, was joint initiator of this study.

AUTHORS’ CONTRIBUTIONS

R.d.J., K.J., V.S. and A.d.B. conceived the research idea and study design. R.d.J., Z.M., K.J. and V.S. were responsible for data acquisition. R.d.J., E.B., N.C., F.B., Z.M., K.J., V.S. and A.d.B. performed data analysis/interpretation. R.d.J., N.C., K.J. and V.S. performed statistical analysis. Supervision or mentorship were performed by V.S. and A.d.B. Each author contributed important intellectual content during manuscript drafting or revision, accepts personal accountability for the author's own contributions and agrees to ensure that questions pertaining to the accuracy or integrity of any portion of the work are appropriately investigated and resolved.

FUNDING

R.d.J., K.J. and V.S. report grants from the European Union (PP-01-2016) and from the European Renal Association during the conduct of the study. The funders did not have any role in study design; collection, analysis and interpretation of data; writing the report and the decision to submit the report for publication. The content of this article represents the views of the authors only and is their sole responsibility; it doesnot reflect the views of the European Commission or any other body of the European Union. The European Commission does not accept any responsibility for use that may be made of the information it contains. This work was presented as an oral presentation at the 58th European Renal Association–European Dialysis and Transplant Association Congress (online, 5–8 June 2021).

CONFLICT OF INTEREST STATEMENT

All the authors have nothing to disclose.

REFERENCES

Author notes