Deaths within 90 days from starting renal replacement therapy in the ERA–EDTA Registry between 1990 and 1992

Dimitri Tsakiris1, Elizabeth H. P. Jones2, J. Douglas Briggs3, Carl-Gusta Elinder4, Otto Mehls5, Shalom Mendel6, Giovanni Piccoli7, Sue P. A. Rigden8, Jose Pintos dos Santos9, Keith Simpson10 and Yves Vanrenterghem11

1 Department of Nephrology, Veria General Hospital, Veria, Greece, 2 ERA-EDTA Registry, St Thomas Hospital, London, UK, 3 Renal Unit, Western Infirmary, Glasgow, UK, 4 Department of Renal Medicine, Huddinge University & Karolinska Intitute, Huddinge, Sweden, 5 Ruprecht Karls Universität Heidelberg, Germany, 6 Tel Aviv University, Israel, 7 Catterda de Nefrologia, Ospedale Molinette, Torino, Italy, 8 Paediatric Nephrology, Guys' Hospital, London, UK, 9 Centro de Hemodialise do Luminar, Lisbon, Portugal, 10 Renal Unit, Glasgow Royal Infirmary, UK, and 11 Department of Nephrology, UZ Gaishuisberg, Leuven, Belgium

Correspondence and offprint requests to: ERA–EDTA Registry, St Thomas' Hospital, London SE1 7EH, UK.

Abstract

Background. Patients who die within 90 days of commencing renal replacement therapy (RRT) may be recorded by some centres and not others, and hence data on mortality and survival may not be comparable. However, it is essential to compare like with like when analysing differences between modalities, centres and registries. It was decided, therefore, to look at the incidence of deaths within 90 days in the ERA–EDTA Registry, and to try to define the characteristics of this group of patients.

Methods. Between 1 January 1990 and 31 December 1992, 78 534 new patients started RRT in 28 countries affiliated to the ERA–EDTA Registry. Their mean age was 54 years and 31% were over 65 years old. Eighty-two per cent of the patients received haemodialysis (HD), 16% peritoneal dialysis (PD) and 2% had pre-emptive transplantation as first mode of treatment.

Results. From January 1990 to March 1993 the overall incidence of deaths was 19% and 4% of all patients died within 90 days from the start of RRT. Among those dying within 90 days 59% were over 65 years compared to 53% over 65 years in those dying beyond this time (P<0.0001). The modality of RRT did not influence the distribution of deaths before and after 90 days. Vascular causes and malignancy were more common in those dying after 90 days, while there were more cardiac and social causes among the early deaths. Mortality from social causes was twice as common in the elderly, who had a significantly higher chance of dying from social causes within 90 days compared to those aged under 65 years. The overall incidence of deaths within 90 days was 3.9% but there was a wide variation between countries, from 1.8% to 11.4%. Finally, patient survival at 2 years was markedly influenced in different age groups when deaths within 90 days were taken into account.

Conclusions. The incidence of deaths within 90 days from the start of RRT was 3.9%, with a marked variation between countries ranging from 1.8% to 11.4%, which probably reflects mainly differences in reporting these deaths, although variable selection criteria for RRT may contribute. Deaths within 90 days were significantly more frequent in elderly patients with more early deaths resulting from cardiac and social causes, while vascular causes of death and malignancy were more common in those dying after 90 days. Patient survival analyses should take into account deaths within 90 days from the start of RRT, particularly when comparing results between modalities, countries and registries.

Keywords: comorbidity; early deaths; elderly patients; mortality; renal replacement therapy; survival

Introduction

In recent years there has been a rapid rise in acceptance rate for renal replacement therapy (RRT) worldwide, resulting in a considerable expansion of the pool of patients receiving treatment for end-stage renal disease (ESRD). Registry data analysis for 1995 showed that the annual rate of expansion in this pool in the European Community, the USA and Japan was 8.2%, 7% and 7.8% respectively, with a total number of patients alive on RRT at the end of 1995 exceeding 700 000 in these three registries [1,2].

This increase reflects a global trend due to improved diagnosis and application of more liberal selection criteria for RRT. Also this increase has resulted in a rise in mean age of the RRT population, more co-morbidity and, in turn, an adverse effect on patient survival which, despite technical advances, has not improved as much as expected. Life expectancy for ESRD patients aged 49 years is similar to that of patients with certain malignancies such as carcinoma of colon [3]. Also the increased acceptance of older and more ill patients has increased early mortality. In the 1991 USRDS report, the mortality within 90 days from starting RRT during 1989 increased from 11% in the 65–69 age group, to 26% in the 85+ age group [4]. In the latter group, the 90-day mortality rose from 21% to 26% between 1983 and 1989, suggesting that comorbidity over this 7 year period was increasing within the 85+ age group accepted for RRT.

In a recent multicentre European study involving seven centres in five countries, a variation in 90-day mortality from the start of RRT was associated with age and comorbidity [5]. In this study overall survival was significantly affected by early mortality, suggesting that deaths within 90 days should be taken into account when comparing results between centres.

Consideration of early deaths is also relevant when comparing survival figures between registries. USRDS reports, for example, consider the survival of patients under 65 years only beyond 90 days for all treatment modalities because of incomplete data documenting early deaths [4]. By contrast, patient survival analyses from the ERA–EDTA Registry include deaths within 90 days, although these events have most likely been under-reported to a variable degree by contributing centres.

It is essential to compare like with like, and for this reason it was decided to define the incidence of and factors related to deaths within 90 days of starting RRT in the ERA–EDTA Registry in order to assess their importance and enable comparisons to be made more accurately with other registries.

Subjects and methods

Between 1 January 1990 and 31 December 1992, 78 534 new patients started RRT in 28 countries affiliated to the ERA–EDTA Registry. The number of contributing centres was 2248, 2344 and 2561 during the years 1990, 1991 and 1992 respectively. The methods of data collection used by the ERA–EDTA Registry have previously been described [6]. Patients with incomplete or erroneous information and seven countries with inconsistent data have been excluded.

The number of new patients entering RRT was 26 647, 26 611 and 25 276 in 1990, 1991 and 1992 respectively. The average response rate to the EDTA patient questionnaire during this period, excluding the above mentioned seven countries, was 83%, 82% and 73% respectively. After 1992 the response rate declined and this was the main reason for studying the years 1990–92.

Males accounted for 46 254 patients (59%) and females 32 280 (41%). The mean age was 54 years and 31% of patients, defined as elderly, were over 65 years old. Of the total, 82% of patients received HD (hospital and home HD), 16% received PD (intermittent, CAPD and CCPD) and 2% had pre-emptive transplantation as first mode of treatment (MOT).

Deaths were recorded between 1 January 1990 and 31 March 1993, and patients were followed up to 31 December 1994.

The tabular analyses compared patients dying within 90 days (day 90 was included in this group) to patients dying after day 90 from the start of RRT. Patients lost to follow-up were included in the tabular analyses, and these comparisons provided results regarding age distribution at start of RRT, sex, first MOT and cause of death. Social causes of death included refusal of treatment, suicide and withdrawal of treatment. Under miscellaneous causes of death are listed 11 causes including malignancy, cachexia, dementia, obstructive airways disease and sclerosing peritonitis. Comparisons between groups were carried out using the Pearson chi-square with Fisher's exact test where appropriate.

Patient survival analyses were carried out within the SPSS using Life Tables, including and excluding deaths within 90 days from start of RRT. Survival of subgroups was compared using the Wilcoxon (Gehan) test. Patients lost to follow-up were excluded. Survival of all patients on RRT was estimated from first MOT to death or to the end of follow-up, and all data on survival were calculated without considering the number of types of RRT used in a given patient. Therefore, patients who started dialysis and subsequently received renal transplants were included in the survival analyses.

Results

Overall incident mortality
The total number of deaths from January 1990 to March 1993 was 14 808 (18.9% mortality of the incident population) (Table 1Go). Of these deaths 3047 occurred within 90 days of starting RRT, which represents 3.9% of the incident population and 20.6% of the total deaths. The remaining 11 761 deaths occurred after 90 days giving a 15% incident mortality and accounting for 76.4% of the total deaths. In Table 1Go columns `% of patients' and `% of deaths' were both calculated with the number of dead patients and they are referred to per cent of dead of the incident population and per cent of total deaths respectively within each of the three categories of deaths within 90 days, over 90 days and total deaths.


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Table 1. Demographic characteristics of the 78 534 new patients of the cohort starting RRT in 1990–1992, and those dying within 90 days and more than 90 days from start of RRT
 
The incident mortality within 90 days in males and females was identical at 3.9%. The proportion of males in those dying within 90 and after 90 days was 59% and 58% respectively.

Mortality within 90 days in the elderly
There was a difference in the mean age (SD) between the two groups of early and later deaths, which was significantly higher in those dying within 90 days at 65.0 (14.0) years compared to 63.1 (14.3) years for those dying after 90 days, P<0.001. The 90-day incident mortality ranged from 0.8% in the <15 age group to 9.8% in the 75+ age group, while the respective mortality from day 90 onwards ranged from 4.8% to 31.2% (Table 1Go). The 55–64 year age group had a mortality of 3.7% and 15.8% within 90 days and after 90 days respectively, which is similar to the overall mortality for all ages in the two groups, 3.9% and 15% respectively. However, in the oldest age groups, 65–74 years and 75+ years, the mortality was significantly higher in those who died within 90 days from the start of RRT. There were more patients aged over 65 years dying within 90 days (59%), compared to those dying after 90 days (53%, P<0.0001) (Figure 1Go).



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Fig. 1. Distribution of deaths within 90 days and beyond day 91 by age groups in new patients starting RRT in 1990–92. Numbers and percentages of patients are shown in Table 1Go. There were significantly more patients over 65 years dying within 90 days compared to those dying beyond day 91, 59% vs 53%, P<0.0001.

 
Primary renal disease and mortality within 90 days

The overall 90-day incident mortality in patients with standard PRD, which includes glomerulonephritis (GN), chronic pyelonephritis, drug nephropathies, polycystic kidneys and hereditary nephropathies was 2.1%. It ranged from 0.9% in hereditary nephropathies to 3.3% in drug nephropathies and was below the average of 3.9% (Table 1Go). This was also the case for those who died after day 90. In both groups mortality due to hereditary nephropathies and polycystic kidneys was the lowest compared with other PRD groups. Also fewer deaths occurred in patients with standard PRD within 90 days compared to beyond 90 days, overall 26.2% against 31.9% (Figure 2Go). There were also fewer deaths in diabetic patients within 90 days at 18.9% compared to 25.4%. In contrast there were more early deaths in patients with unknown PRD, renovascular disease (RVD), multisystem and miscellaneous diseases, 18% compared to 14.3%, 17.2% compared to 15.8%, 10.4% compared to 7.8% and 9.3% compared to 5.4% respectively.



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Fig. 2. Distribution of deaths within 90 days and beyond day 90 by primary renal disease in new patients starting RRT in 1990–92. Numbers and percentages of patients are shown in Table 1Go. Standard PRDs and diabetes were less frequent, while unknown PRDs, RVDs, multisystem and miscellaneous diseases were more common in patients dying within 90 days compared to those dying beyond day 90.

 
First MOT and mortality in 90 days
The 90-day incident mortality for HD and PD did not differ from the overall average in the two groups (Table 1Go). In the small number of patients who had pre-emptive transplantation as first MOT the incident mortality was much lower at 1.3% and 1.8% within and beyond 90 days respectively although the percentage of total deaths accounted for by pre-emptive transplantation was three times higher within (0.7%) than beyond (0.2%) 90 days (Table 1Go).

Causes of death
Cardiovascular causes were responsible for more than half of the deaths. The causes of death within and beyond 90 days are shown in Table 1Go and Figure 3Go and the subdivision of causes under the heading of cardiac and vascular are shown in Table 2Go. Vascular causes of death, 60% of which were due to cerebrovascular accident, and malignancy were more common in those patients dying after 90 days compared to those dying within 90 days, 15% vs 12.4% (P<0.00025) and 6.5% vs 5%, (P<0.0016 respectively). By contrast, more deaths due to cardiac and social causes occurred within 90 days, 41.2% vs 38.6% (P<0.009) and 5% vs 4.2% (P<0.01) respectively. Although the difference seems small, social causes of death were more common within than beyond 90 days (5% vs 4.2%: P<0.01) as shown in Table 2Go.



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Fig. 3. Distribution of deaths within 90 days and beyond day 90 by causes of death in new patients starting RRT in 1990–92. Numbers and percentages of patients are shown in Table 1Go, and Table 2Go. Cardiac and social causes of death were more frequent in patients dying within 90 days, while vascular and miscellaneous causes, including malignancy, were more common in those dying beyond day 90.

 

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Table 2. Deaths due to cardiac, vascular, social causes and malignancy in new patients starting RRT in 1990–1992
 
Mortality from social causes was more than doubled in the elderly. Of the deaths due to social causes 5.7% occurred in patients over 65 years and the remaining 2.7% in the younger patients. Within this group withdrawal of treatment accounted for 3.2% and 1.2% of deaths in the older and younger patients respectively. Furthermore patients over 65 years had a higher chance of dying from social causes within the first 90 days than beyond this time, 82% against 69% (P<0.01) (Figure 4Go).



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Fig. 4. Social causes of death (n=646) in new patients starting RRT in 1990–1992. Elderly patients had a significantly higher chance to die from social causes within 90 days of commencing RRT compared to those after day 90, 82% vs 69%, P<0.01.

 
Variation between countries in the 90-day mortality
Table 3Go shows the incidence of deaths within 90 days in the countries included in this study. The average incidence was 3.9% and there was a wide variation from high figures in Norway and Sweden at 11.4%, down to countries including Greece, Ireland, Spain and Switzerland with an incidence of around 2%. Lack of uniformity in reporting deaths to the Registry is thought to be the major reason for these differences although different selection criteria in the acceptance of patients for RRT may have contributed.


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Table 3. Incidence of patients dying within 90 days from start of RRT in different countries
 
Patient survival
Figure 5Go shows that patient survival at 2 years was markedly influenced by age when deaths within 90 days are taken into account. The difference in survival depending on whether early deaths were included or not was 3.3% in the total patient group but was much less in the 35–55 year age group, at 1.6% and by contrast was greater at 5.5% in the elderly patients.



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Fig. 5. Patient survival at 2 years including and excluding patients dying within 90 days from start of RRT in the overall cohort, in the age group 35–55 and over 65 years. It is apparent that by excluding the early deaths in the high risk group of elderly patients their survival improved by 5.5%, P<0.0001.

 
Discussion

One of the most striking findings in this study is that 4% of patients starting RRT during 1990–1992 died within 90 days of commencing therapy, accounting for about 20% of all deaths.

In recent years a global trend of applying more liberal acceptance criteria for patients entering RRT has resulted in a marked expansion of the ESRD pool, a large fraction of which now consists of elderly patients with co-morbid factors. In the ERA–EDTA Registry the proportion of patients aged over 65 years rose from 3% in 1971–1975 to 18% in 1981–1985 [7] and to 31% in the 1990–1992 cohort of this study. The Registry did not in the past gather information on extra-renal comorbid factors at the start of RRT, which together with age are the most important determinants of death. However, as the cause of ESRD is one of the strongest predictors of mortality [3,4], an indirect measure of the greater comorbidity comes from the increased proportion of patients with RVD and multisystem diseases (including diabetes) accepted for RRT, which rose from 7.6% and 10.8% in 1979 [8] to 12.3% and 19.1% respectively in this 1990–1992 cohort.

In 1989 the 90-day incident mortality in the USA for elderly RRT patients was much higher than in Europe, ranging from 11% in the 65–69 year age group to 26% in the 85+ age group [4]. For younger patients there have been no statistics from USRDS, nor has any other national registry reported results on this topic.

The only reports on early deaths come from single centre and small multicentre studies on both sides of the Atlantic. Wright, in a single centre study of 138 patients, reported that 32% of all deaths occurred within 90 days from the start of RRT [9]. Using a simple classification scheme based on age and comorbidity, he successfully predicted the risk of early deaths and identified a group of patients predicted to do well. Khan et al., adopting the same risk stratification criteria in two units in Scotland, reported an identical figure of 32% in a population of 375 patients. The overall survival of this group was 65% at 2 years but this masked a wide spread of survivals, ranging from 35% in the high risk group to 86% in the low risk group [10]. Khan et al. extended these findings in a multicentre study involving seven European centres, reporting an overall 90-day mortality of 8.7%, and emphasizing the need for uniform methodology in the collection and analysis of data to enable valid comparisons to be made between centres and registries [5].

There has also been a problem in comparing registry data not only because of variations in the quality of the data but also because of differences in the methods applied to mortality and survival analyses. For example, USRDS reports exclude deaths from 0 to 90 days in patient survival probabilities [4], in the Canadian haemodialysis morbidity study, the eligibility criterion was survival on HD for 1 month from initiation of therapy [11] and ERA–EDTA Registry reports have included 90-day mortality in their survival analyses.

Although both in the general population and among dialysis patients females had a lower overall mortality rate in Europe [12,13] and in the USA [4] compared to males, this study shows that the 90-day mortality was identical between males and females. This suggests that factors which contribute to better survival for females in the long-term do not apply to early deaths.

As expected, there was a strong association between 90-day mortality and old age. In the age groups up to 45–54 years, early mortality was much lower when compared to the overall average of 3.9%. For the age group of 55–64 years early mortality was close to the average, but for the oldest age groups of 65–74 and 75+ years it increased significantly to 6.3% and 9.8% respectively (Table 1Go). In the USA the 90-day mortality for 1989 was nearly double that in Europe, 12.5% for the 65–74 age group and 21% for the 75+ age group [4]. Also in the USA early mortality in the oldest age group (85+ years) increased from 21% to 26% between 1983 and 1989, suggesting that comorbidity within this age group in patients accepted for RRT was becoming more pronounced over these 7 years.

The cause of ESRD is one of the strongest predictors of mortality. Diabetic patients on RRT have approximately twice the mortality risk compared to patients with glomerulonephritis [3]. In the 1985 incident cohort of USRDS, the age, race and sex adjusted patient survival (after 90 days) at 5 years was 49% in patients with primary renal diseases e.g. glomerulonephritis, 41% in patients with hypertension and 24% in diabetic patients [4]. Similar results were reported from the ERA–EDTA Registry (including deaths within 90 days) in patients starting treatment since 1980, with the best 5 year survival in patients with polycystic disease and progressively lower survival in those with glomerulonephritis, pyelonephritis, RVD and diabetes [12]. In this study the 90-day incident mortality was 2.1% in patients with standard primary renal diseases and three times higher at 6.4% in patients with RVD, diabetes, multisystem and miscellaneous diseases (Table 1Go). Patients with polycystic kidneys and hereditary nephropathies were the least likely to die within 90 days among those with all causes of ESRF, while diabetic patients were at a higher risk of dying within 90 days compared to patients with standard PRD (Table 1Go), although the proportion of deaths in diabetic patients dying beyond day 90 was higher than for those dying within 90 days (Figure 2Go).

With regard to first MOT, there was no major difference in the 90-day incident mortality between patients receiving HD or PD (4% vs 3.7%) as first treatment. By contrast, Innes et al. reported significantly greater use of HD compared to CAPD in patients dying early [14]. They related these deaths to late referral with the need for emergency haemodialysis and stressed the importance of nephrological assessment before the patient reached ESRD. The proportion of deaths within 90 days in patients undergoing pre-emptive transplantation as first MOT was three times higher in this study compared to deaths beyond day 90, due presumably to causes related to the operation and early post-operative period.

More than half of the total deaths in the 1990–1992 incident cohort were due to cardiovascular causes, followed by miscellaneous causes and infections. Cardiac and social causes of death were more common in those dying within 90 days, while vascular causes and deaths from malignancy were more common beyond day 90 (Tables 1, 2GoGo, Figure 3Go). In the 1991 USRDS report cardiac causes of death also predominated between days 0 and 90 in patients over 65 years, but withdrawal of treatment was the next most common, both in the first 90 days and overall.

Furthermore, these deaths in the USA increased from 1.6 per 1 000 patient years in the 45–64 age group to 9.6 in the 65–74 age group and to 19.4 in the 75+ group [4]. In our study deaths from withdrawal of treatment represented 2.3% of the total deaths (341 from 14 808) and were more common in patients >65 years (3.2%) compared to those <65 age group (1.2%) but these figures are much lower than in the USA. The high rates of dialysis withdrawal in the USA may be due in part to acceptance of more very old patients with multiple comorbid factors. Also, in the USA patients developing ESRD after the age of 65 are immediately eligible for Medicare coverage and the USRDS data are therefore likely to be more complete in comparison with the voluntary ERA–EDTA Registry.

In this analysis the 90-day mortality ranged from 1.8% in Ireland to 11.4% in Norway and Sweden. In a previous Registry report which compared patient survival (including deaths within 90 days) of elderly patients in selected countries, it was noted that in Nordic countries half of the patients had died by the end of the first year as opposed to other European countries in which patient survival was around 70% to 80% [15]. Acceptance rates did not appear to differ between Nordic and other selected countries, although there was a higher prevalence of diabetic nephropathy and more transplanted patients in the older age groups in the Nordic countries. In this study, acceptance of diabetic patients for RRT varied widely from 1% in Romania to 25% in Finland. However, this could only partly explain differences in 90-day mortality, which was higher in diabetic patients compared to those with standard PRD, as significantly more diabetic patients died beyond day 90. Nevertheless, these points suggest that different selection criteria for RRT, as well as variations in comorbidity, do exist across countries in Europe. In a recent review on evolution of RRT in central and eastern Europe, Rutkowski et al. reported that availability of these facilities varied widely between these countries and described a dramatic change in recent acceptance of ESRD patients [16]. In this cohort among the five countries of central and eastern Europe, Romania, which appeared to have the strictest selection criteria for RRT, had the lowest 90-day mortality rate at 2.9%, while Hungary, with the larger fraction of elderly patients, had the highest at 5.8% amongst these countries (Table 3Go). Yet none of these countries were among those with the lowest 90-day mortality in Europe, such as Ireland, Greece, Spain and Switzerland. Most likely this is because, apart from patient related factors such as comorbidity which may influence outcome, treatment related factors and possibly a centre effect are also important for patient survival. Such a centre effect was described in the Biomed multicentre study by Khan et al. [5]. In that study the 90-day mortality rate ranged from 2.7% to 13.1% across seven centres in five European countries, which is similar to the range observed in this study. Stratification of patients to a low, medium and high risk group based on age and comorbidity revealed a variable fraction of high risk patients among centres ranging from 13.7% to 34.1%. Comparison of patient survival among centres revealed significant differences which lessened after exclusion of early deaths from analysis, although they did not disappear, suggesting the presence of a centre effect.

In this study patient survival at 2 years of the overall cohort and that of the 35–55 years and over 65 years age group, showed a significant influence of early deaths on survival. In the latter group, where most of the early deaths occurred, survival was 67.1% and improved to 72.6% when deaths within 90 days were excluded. A similar effect was reported by USRDS, where patient survival at 2 years improved from 51.8% to 54.7% when 90-day mortality was excluded [4].

Patient survival coupled with quality of life are the most important measures of outcome for patients receiving RRT. In order to evaluate this outcome we need to establish standards and audit measures in providing health care for ESRD patients along the lines described by Gokal in a recent editorial comment [17]. Such standards are less meaningful if we do not possess a common methodology which will enable us to identify high risk patients and compare survival rates both between centres and between countries.

In conclusion, deaths within 90 days of commencing RRT in Europe showed a wide variation between countries and this probably reflects differences mainly in reporting these deaths, although differing selection criteria may contribute. Patients dying very soon after the start of dialysis include a population to whom more liberal acceptance criteria have been applied. It is essential that national and international registries establish uniform methods of data collection which will take into account case-mix variation and the effect of early deaths in the comparison of survival between modalities, centres and countries.

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Received for publication: 29. 9.98
Accepted in revised form: 22. 6.99