NDT Plus 2008 1(Supplement 4):iv2-iv5; doi:10.1093/ndtplus/sfn115
© The Author [2008]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org
Prevalence of nephropathy in the German diabetes population—Is early referral to nephrological care a realistic demand today?
Wolfgang Pommer
Department of Internal Medicine-Nephrology, Vivantes Humboldt Hospital, Berlin, Germany
Correspondence: Wolfgang Pommer, Department of Internal Medicine-Nephrology, Vivantes Humboldt Hospital, Am Nordgraben 2, D-13509, Berlin, Germany. Tel: +49-30-13012-2170; Fax: +49-30-13012-2186; E-mail: wolfgang.pommer{at}vivantes.de
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Abstract
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In Germany, diabetes mellitus in the general population has
increased to
8 million people. The implication of this trend
for future nephrological care is not well known, as data on
this issue are rather limited. Results from different population-based
studies suggest that microalbuminuria in diabetic patients is
present in 20–30% of the cases. Findings from the diabetes
disease management programme in the North-Rhine area revealed
the prevalence of chronic kidney disease (CKD) stage II in half
of the participants (CKD stage III was present in
20%). Only
a small proportion of this cohort (
1–2%) will reach end-stage
renal failure, probably due to the excess mortality risks attributed
to advanced kidney disease. Results from the QUASI-Niere registry,
which reports on renal replacement therapy in Germany, indicate
almost constant incidence and prevalence rates of diabetes in
the last 5 years (30.6–34.2% and 23.6–27.1%, respectively).
The high percentages of early stages of CKD in the diabetes
population indicate a potentially high burden of future nephrological
care, especially if patients are referred to nephrologists at
an early stage. In reality, in nephrological care, bearing this
burden is impossible without expanding the resources for this
patient group.
Key Words: chronic kidney disease • diabetes mellitus • health costs • nephrological care • referral politics
Received for publication March 6, 2008. Accepted for publication June 19, 2008.
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Introduction
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The recognition of a worldwide pandemic of diabetes mellitus,
predominantly type 2 diabetes, is alarming health care officials
and the general public. In Germany, about 7 million people are
known to have manifested diabetes mellitus, 2 to 3 million are
thought to have undetected disease and about 10 million people
are diagnosed having impaired glucose tolerance [
1]. Between
1988 and 2000, treated cases of diabetes have increased by 43%
[
2]. Data from regional surveys in Germany suggest that for
every detected case with diabetes one case goes undetected [
2].
It is suspected that in the near future every third person in
the age group over 65 years will suffer from diabetes mellitus.
Despite current efforts to integrate a substantial number of
patients into structured disease management programmes (DMPs),
a systematic analysis of diabetic patient care in Germany reveals
distinctive deficits in transferring recommendations and guidelines
into daily patient care [
3].
The most important complication of diabetes mellitus is end-stage renal disease (ESRD), accounting for the largest part of the financial burden of diabetes. Although from the patient's view, this complication is one of the most frightening, the high mortality related to the severely increased risk of cardiovascular complications in the stages preceding dialysis is the most important issue in preventive diabetes care. Two cohort studies in both type 1 and type 2 diabetes have found that the likelihood of death from cardiovascular events is about 12 times higher than ESRD [4,5]. Additionally, data from the UKPDS study provide evidence that yearly mortality rates are higher than the rate of progression from one stage of kidney disease to another [6]. Because albuminuria and impaired renal function are both well-established risk factors of cardiovascular morbidity and mortality [7], preventive care in diabetes patients will have to focus on these symptoms. Current guidelines recommend early referral to the nephrologist if serum creatinine exceeds the upper normal limit or hypertension is uncontrolled and antihypertensive therapy has failed to reach the target values [8]. To estimate the burden of nephrological care, data on the early stages of diabetic nephropathy are warranted. As in most other countries, in Germany, these data are not systematically evaluated and published although the routinely collected data of the DMPs would provide an excellent source to measure effects of current intervention. This paper summarizes the outcome of diabetic nephropathy from the available population-based studies of different regions in Germany, and includes findings from a so far unpublished data set of the DMPs in the North-Rhine area.
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Definition of nephropathy in diabetic patients
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Nephropathy in this context is defined as albuminuria of any
degree (in most subjects detected by microalbuminuria screening)
and renal insufficiency as calculated by formula clearances
(Cockroft–Gault or MDRD). Stages of chronic kidney disease
(CKD) are classified by renal function (creatinine clearance
in ml/min) as defined by current DOQUI guidelines [
9]. Therefore,
in this context, nephropathy is not necessarily restricted only
to diabetic glomerulosclerosis but also to a high proportion
of different diseases; frequently, hypertension and macrovascular
complications are present [
10–12].
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Data on stage I–IV nephropathy in diabetic patients
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Results on early stages of nephropathy are evaluated in four
different study populations. Six hundred diabetic patients recruited
from 58 representative outpatient diabetic centres in Bavaria
were screened for albuminuria [
13]; microalbuminuria was detected
in 19.6% in type 1 and 17.2% in type 2; macroalbuminuria was
present in 10.8% of the cases (11.7% in type 1 and 7.8% in type
2 diabetes patients). In the KORA study, a random population
sample ranging from ages 25 to 74 years showed proteinuria in
19% of the group with type 2 diabetes while 0.7% of the cases
underwent dialysis [
14]. In a representative study on the prevalence
of hypertension and diabetes (HYDRA study), 45 000 patients
from 1912 general practitioners were screened [
15]. Diabetes
was detected in 32% of the men and 28.3% of women. Of these,
37.8% of the patients with diabetes and hypertension tested
positive for microalbuminuria. Microalbuminuria was prevalent
earlier in only 12.5% of the cases. It can be estimated from
these study populations that at least 30% of the diabetes patients
in a primary care setting may have CKD stage I (Table
1).
Recent findings from a group of customers of a German insurance
company screened for diabetes showed the presence of microalbuminuria
in 18% of the cases and a renal clearance <90 ml/min/1.73
m
2 in 89% of the cases, which is predominantly CKD stages II
and III [
16].
Currently, about 2 million patients in Germany are included in one of the several diabetes DMPs. Data from more than 50 000 diabetic patients screened in the North-Rhine area were analysed by time under observation and stage of CKD (calculated by the Cockroft–Gault formula) (Altenhofen et al. personal communication). The stage of kidney disease increased with time of observation. In the observation period of 5 years, CKD stage II was found in 35% of the cases (>5–10 years, 37%; >10 years, 38%). The proportion of CKD stage III increased gradually with time (<5 years, 16%; 5–10 years, 20%; >10 years, 28%) while that of CKD stages IV and V remained almost unchanged independently from the time of observation (Figure 1). We believe that this finding reflects the high mortality risks of the diabetic population in the advanced stages of renal disease as discussed above.
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End-stage renal failure in patients with diabetes mellitus
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Best evidence of the development of renal replacement therapy
is provided by the German registry QUASI-Niere [
17]. At the
end of 2004, about 61 000 patients were reported undergoing
dialysis therapy; more than 21 000 were alive with functioning
grafts. The prevalence and incidence of diabetic patients increased
moderately from 21.6% (respectively 30.6%) in 1996 to 27.1%
(respectively 34.2%) in 2004 (Table
2). In the last 5 years,
the incidence of diabetes in the end-stage renal population
remained almost unchanged and exceeded by the increasing trend
in vascular nephropathy (Figure
2). In the QUASI-Niere cohort,
age-specific mortality of diabetic patients in the age over
75 years is almost identical with the non-diabetic group (Figure
3). This cohort does not include cases that are withheld from
dialysis therapy or refused to start dialysis treatment. Furthermore,
unreported cases with early mortality within the first months
of dialysis are missed.
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Table 2 Incidence and prevalence of diabetes mellitus in the German dialysis population: data from the QUASI-Niere registry (2005)
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Are German nephrologists ready to carry the burden of diabetic patients?
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Every patient with nephropathy should be screened by a nephrologist.
This is completely true in patients with diabetes and nephropathy.
While in the early stage of nephropathy distinctive diagnosis
of the underlying renal disease has to be established and specific
treatment options have to be offered, if available, nephrological
care in the advanced stages of CKD must focus on slowing the
progression of kidney disease and treating secondary complications.
Applying the data on nephropathy in diabetic patients into the
reality of medical care, a tremendous workload must be borne
by German nephrologists. Arbitrary calculations according to
the current guidelines on diabetic care result in 2000–4000
appointments per year for each practising nephrologist (Table
3). Although the contribution of nephrological care in diabetic
patients is based on evidence [
18], this burden of care is intolerable.
Without increasing resources, the demand for early referral
of diabetic patients to nephrological care remains a problem.
A similar situation was recognized recently in Italy [
19].
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Summary and perspectives
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About 8 million people in Germany suffer from diabetes mellitus.
About one-third of them are considered to have some type of
kidney disease reflected by albuminuria and decreased renal
function. From the estimated number of 1.5 million cases with
CKD stage III, a small proportion is progressing to stages IV
and V of kidney disease (see Table
1). Only 2000 diabetic patients
yearly were accepted for renal replacement therapy. This may
reflect the high mortality rates in patients with diabetes and
chronic kidney disease. Despite the fact that diabetes mellitus
contributes to the biggest proportion of patients starting dialysis
therapy, incidence rates of ESRD in this group remained stable
in the last 5 years. This is in contrast to the growth of diabetes
cases in the general population. The conclusion that the increase
in diabetes in the general population leads to a rising tide
of diabetic patients on dialysis is not substantiated by the
available data.
This observation may reflect both good and bad news: the bad news is that we do not sufficiently care for mortality risks attributed to nephropathy before reaching ESRD; the good news is that retarding progressive kidney disease extends lifespan before dialysis and keeps patients off from the experience of the sad truth of living a life with dialysis. Besides this, without expanding the number of nephrologists and the resources needed to manage their patients, early care for diabetes patients with nephropathy in Germany remains a wishful thinking so far.
Conflict of interest statement. None declared.
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Abstract
Introduction
