1 Division of Nephrology and 3 Quality of Care Unit, University Hospital of Geneva, 2 Division of Nephrology and 4 Quality of Care Unit, University Hospital of Lausanne, Switzerland and 5 Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania Medical Centre, Philadelphia, PA, USA
Correspondence and offprint requests to: P. Saudan, Division of Nephrology, University Hospital, 1211 Geneva 14, Switzerland. Email: Patrick.Saudan{at}hcuge.ch
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Abstract |
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Methods. A cross-sectional study of 617 dialysis patients treated at 19 facilities examined the distribution of indicators of quality of care addressing: adequacy of dialysis (Kt/V 1.2 for haemodialysis, Kt/V
2 for peritoneal dialysis), anaemia control (haemoglobin
110 g/l), calcium and phosphate control (product
4.4 mmol2/l2), adequate nutrition (serum albumin >35 g/l), hypertension control (pre-dialysis blood pressure <140/90 mmHg) and type of vascular access. Centre quality targets were the following: achievement of quality criteria for 80% of their patients, except 85% for anaemia control and 60% for arterio-venous fistulae.
Results. Most centres fulfilled quality targets for dialysis adequacy, but substantial variations existed among centres (haemodialysis, 76%, range 36100; peritoneal dialysis, 76%, range 33100). Results were similar for anaemia (77%, range 35100), calcium x phosphate product (69%, range 2992), albumin (63%, range 2695), hypertension control (33%, range 1354) and arterio-venous fistula (61%, range 4992). The between-centre variability was significantly greater than would be expected by chance, for all indicators. Dialysis facilities with >40 patients better fulfilled quality targets than university-based centres. Adjustment for patient characteristics did not modify these results.
Conclusions. Substantial variations in quality indicators existed between dialysis centres in western Switzerland, which could not be attributed to different centre policies, or to differences in available measures of patient case mix. These findings indicate opportunities for improvement in dialysis practice which may translate into improved clinical outcomes.
Keywords: dialysis; end-stage renal failure; quality assessment; quality of care
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Introduction |
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Earlier studies have revealed striking regional differences in the distributions of such indicators, both across dialysis networks in the USA [8] and among countries in international comparisons [9]. The differences are not fully explained by patient characteristics, suggesting variations in the quality of care. However, studies that focus on regional or national averages fail to capture possible differences in quality indicators between dialysis centres within a given region. Between-centre variations in quality of care have received only limited attention so far. In particular, a recent study has shown that the implementation of a quality improvement programme reduces between-centre variability in quality indicators [10]. Understanding between-centre variability in clinical performance is important for the identification of best practices in dialysis care.
The aim of the present study was to compare quality of care indicators between dialysis facilities in an areawestern Switzerlandwhere access to health care is virtually unrestricted, and where the population is culturally and ethnically homogenous. Furthermore, we adjusted these comparisons for patient characteristics, in order to clarify whether patient case mix could explain part of the observed differences in quality indicators.
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Subjects and methods |
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Study design
A cross-sectional evaluation of all patients with end-stage renal failure (ESRF) on all forms of chronic dialysis was performed in March 2001 for the 18 French-speaking centres and in June 2001 for the three German speaking-centres. Two months prior to the study, a resource guidebook was provided to the centres, containing selected internationally recognized guidelines and recommendations on dialysis quantity and modalities, anaemia, nutritional status, calcium and phosphate metabolism and vascular access [3,1215]. A multidisciplinary team of the University Hospitals in Geneva and Lausanne led this project. Participation of all dialysis centres was voluntary. The project was approved by the research ethics committees of the Universities of Lausanne and Geneva.
Data collection
We collected patient-level data by means of a questionnaire, completed by the centre team based on each patient's medical and nursing records, and centre-level data using a questionnaire, completed by the medical director and head nurse. In addition, patients filled in a self-report questionnaire regarding their satisfaction with their care and health status, the results of which will be reported elsewhere.
Patient-level data
Quality criteria were defined for individual patients in six domains of clinical care:
To better understand the aetiology of possible deviations from the recommended criteria for some of the quality indicators, we also recorded the mean dose of recombinant human erythropoietin per week and its mode of administration, measurements of ferritin and transferrin saturation, levels of serum alkaline phosphatase and serum intact parathormone (PTH), use of phosphate binders and vitamin D, the body mass index, and the date of creation and type of vascular access (arterio-venous fistula, graft, tunnelled and non-tunnelled catheters).
Finally, we also requested for each patient descriptive and clinical data: age, gender, time on renal replacement therapy, current dialysis modality, pre-dialysis nephrologist referral, placement on waiting list for transplantation, cause of renal failure and presence of medical conditions that allow computation of the modified Charlson co-morbidity index. This index gives a score of 1 for all forms of coronary artery disease as well as congestive heart failure, peripheral vascular and cerebrovascular diseases, dementia, chronic pulmonary disease, connective tissue disorder, peptic ulcer disease, mild liver disease and diabetes. Hemiplegia, diabetes with organ damage, any tumour, leukaemia and lymphoma received a score of 2. Moderate or severe liver disease were scored 3, and AIDS or metastatic solid tumour were scored 6. We added 2 for ESRF and 1 for each decade >40 years of age. This index was recently validated for predicting outcomes and costs in dialysis patients [16].
Centre-level data
Centre-level data were obtained by averaging values across all patients treated by each centre. Percentages of patients expected to fulfil a quality criterion (quality targets) were derived from Canadian and European guidelines for anaemia management (85%) and native fistula prevalence (60%). They were set arbitrarily to 80% for dialysis adequacy, calcium and phosphate metabolism, and nutrition.
Furthermore, we obtained a description of each centre for routine clinical practices such as target dose of delivered dialysis, anaemia treatment, calcium/phosphorus management policies, vascular access monitoring and blood pressure control (Table 1).
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We used logistic regression modelling to determine if patient characteristics influenced between-centre comparisons. The dependent variable was the fulfilment of each quality of care criterion, and the regression coefficients for each centre were adjusted for patient age, gender, duration of dialysis and Charlson co-morbidity index. We derived the adjusted proportions of patients who fulfilled each quality criterion from these models. Then, we computed a Pearson correlation coefficient between the unadjusted and the adjusted proportions. To take into account intra-centre characteristics, we performed an analysis that considered each centre as a cluster of observations using a generalized estimating equation. This procedure estimates SEs that are corrected for lack of independence between observations.
All data analyses were performed using SPSS for Windows (version 11.0, Chicago, IL) and Stata (version 8.2; College Station, TX).
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Results |
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Centre characteristics
Centres treated a median of 23 haemodialysis patients (range 675), and were equipped with a median of 10 dialysis beds (range 326, total 190). There were two University-based centres which treated 158 patients in total, five centres with 40 patients which treated 238 patients and 12 centres with <40 patients which treated 221 patients. In the nine units performing peritoneal dialysis, a median of six peritoneal dialysis patients (223, total 64) were treated per centre. Median nursing workload was 54 dialysis sessions/nurse/month (range 3368).
Median medical staffing was 0.5 physician/10 patients (range 0.11.1) (Table 2).
All units had reverse osmosis-based, water preparation systems, and all implemented mixed (heat and chemical) disinfection procedures of the water treatment system. Routine measures for infection prevention (vascular access care, patient isolation and vaccination procedures) were comparable among the centres, but routine vaccination against pneumococcus was implemented in only nine centres. Only one centre had a dialyser reuse policy. The target dose of delivered dialysis (sp Kt/V) was 1.2 for 17 centres,
1.4 for three centres (one centre did not specify a target dose) and/or URR
65% in all units. All centres treated anaemia with erythropoietin (subcutaneously in 94% of the patients) and intravenous iron, with a target haemoglobin of 110 g/l in 15 centres and 100 g/l in four centres (two centres did not specify a target dose). Iron stores were considered adequate when the ferritin level was >200 IU/l in 13 centres. All centres aimed to maintain serum phosphorus levels below 2 mmol/l and calcium levels between 2.25 and 2.50 mmol/l, with the help of phosphate binders and vitamin D. Aluminium salts were not used routinely. As no specific guidelines on blood pressure control in dialysis patients were available at the time of the study, hypertension control was characterized as a pre-dialysis blood pressure of <140/90 mmHg according to JNC VI.
Patients characteristics
Almost all patients (98%) were Caucasian, a slight majority was male, and the mean age was 64 years (Table 3). Hypertensive nephropathy was the leading cause of ESRD, and vascular disease was the most prevalent co-morbid condition. Diabetes was diagnosed as the main cause of ESRD in 15% of our patients but, when included as a co-morbidity factor, was present in nearly one-third of them. The mean modified Charlson index was 7.6 (SD 3.1).
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Quality of care indicators
For all six indicators, the majority of patients satisfied the individual quality criteria, with proportions ranging from 61% (arterio-venous fistula) to 77% (for anaemia control), save for control of hypertension which was only 33% (Table 4). However, the conformity rate varied considerably across centres (Figure 1). This variation was statistically significant for all indicators (all P<0.001). Less than half of the dialysis centres fulfilled each of the centre quality targets (Table 4). Overall, no centre fulfilled all six centre quality targets, one (5%) fulfilled four targets, three (16%) fulfilled three targets, nine (47%) fulfilled two targets, five (26%) fulfilled one target and one (5%) centre fulfilled none.
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Differences in the prevalence for three indicators (absence of anaemia, albumin and Kt/V) were found between larger (>40 patients) dialysis units vs smaller units and university-based dialysis units (Table 5).
Using university-based dialysis units as the reference group, odds ratios for absence of anaemia were 2.2 [95% confidence interval (CI) 1.14.5] in the >40 patients dialysis units and 0.8 (95% CI 0.41.5) in the <40 patients dialysis units. For normoalbuminaemia, odds ratios were 6.4 (95% CI 1.922.1) in the >40 patients dialysis facilities and 1.0 (95% CI 0.42.9) in the <40 patients dialysis units.
For dialysis adequacy, odds ratios were 2.1 (95% CI 1.04.6) in the >40 patients dialysis facilities and 1.6 (95% CI 0.83.2) in the <40 patients dialysis units.
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Discussion |
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Several patient characteristics were associated with the achievement of quality criteria. In particular, men were more likely than women to have an arterio-venous fistula, and healthier patients were less likely to be anaemic. Patients with the briefest duration of ESRD in our population were less likely to suffer from hypoalbuminaemia, which is in agreement with a previously published observation [17]. Adjustment for patient characteristics changed centre-level results very little. This suggests that the dialysed population in the participating centres is similar, and that in this particular instance, adjustment for patient case mix is not necessary for meaningful between-centre comparisons. We found that centres having >40 patients scored better than university-based centres in terms of dialysis adequacy, absence of anaemia and normoalbuminaemia. These better results probably reflect the increased prevalence of incident patients in the university-based dialysis centres. The differences between centres with >40 patients and smaller centres is more difficult to explain since neither centre policies nor patient characteristics appear to explain this variation. In particular, the great variability in human resources among the centres did not correlate with the variation observed in quality of care indicators (Table 2). The availability of the nephrologist may play a role since in the larger centres the medical staff are more important. Another possible explanation is that the patient characteristics included in our adjustment models failed to include important determinants of quality indicators, and that better adjustment models would have decreased residual inter-centre variability. However, it is unclear to us what these hidden confounding variables might be. An alternative explanation could be that centre policies as reported do not truly reflect how care is delivered to patients in daily practice, and that these clinical practices vary from one centre to another despite stated policies being globally the same. Furthermore, differences in family support or income may also contribute to the variation in the achievement of quality criteria. Unfortunately, we did not obtain this information in our study. Other explanations have to be found for the well-known hurdles to translate guidelines into clinical practice, i.e. resources availability, physician behaviour, etc.
Generally, the results observed in the western Swiss centres matched those observed elsewhere. Dialysis adequacy in our patients (both haemodialysis and peritoneal dialysis 76%) was midway between the levels observed in the USA (haemodialysis 86%, peritoneal dialysis 69%) and The Netherlands (haemodialysis 59%) [18,19]. Our patients were slightly older than their US counterparts, but the proportion of patients with a functional arterio-venous fistula is considerably higher than in the USA. We believe that adequacy of dialysis should improve in our region as nephrologists become more aware of the recommended threshold for the Kt/V.
Anaemia management in our patients nearly reached the target identified by the European Best Practice Guideline (EBPG) 5 (target of >11 g/dl for 85% of the population) [3,20]. Two factors may have contributed to this finding. First, European guidelines on anaemia treatment were published in 1999, well before our study was conducted, and anaemia treatment in haemodialysed patients has received much attention in the interim. Secondly, most facilities in our area also participated in the European Survey on Anaemia Management (ESAM) study in the 1990s. Understandably, most of our nephrologists were fully aware of the haemoglobin target of 110120 g/l in this population.
Calcium and phosphate metabolism as well as the nutritional status of our patients were areas with the largest opportunity for improvement. One-third of our patients had an elevated serum calcium x phosphate product. Similar results have been reported in Italy [21]. These parameters have been linked to an increased risk of cardiovascular mortality, and lowering their levels in dialysed patients is crucial. However, mild phosphate and calcium disturbances are often asymptomatic, and aggressive use of phosphate binders and active vitamin D sterols to treat secondary hyperparathyroidism and hyperphosphataemia is commonly hampered by the risk of hypercalcaemia.
Hypo-albuminaemia was observed in 37% of our patients, well above the 20% found in a French cooperative study [17]. Although serum albumin was shown to predict mortality in dialysis patients, it is also related to factors other than nutrition, such as liver disease and inflammatory states. It also has to be mentioned that the nephelometric method which gives lower results was used in almost all units. Nevertheless, the absence of a nutritional assessment by two methods in nearly 80% of the patients and absence of widespread nutritional support indicate a deficiency in care. Indeed, a dietitian was available only part-time in most of the facilities, which may explain the fairly low standard of nutritional care in our patients.
Concerning vascular access, our results (61% patients with an arterio-venous fistula) are midway between European (80%) and American (24%) results reported by the Dialysis Outcomes and Practice Patterns (DOPPS) survey [22]. Fistula prevalence varied considerably among centres in our area, ranging from 49 to 92% of the patients. This probably reflects local habits or availability of surgeons dedicated to arterio-venous fistula surgery, but may also reflect a lack of implementation of guidelines in some centres. Blood pressure seems adequately controlled in only one-third of our patients. Moreover, cardioprotective medications such as angiotensin-converting enzyme inhibitors (ACEIs)/angiotensin II receptor blockers and ß-blockers were given only to one in three patients in our dialysed population (Table 6). As these medications have been proven to reduce the elevated cardiovascular mortality in these patients, their use should be more widespread in dialysis patients.
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Our study has several strengths and limitations. The cross-sectional design does not afford a prospective assessment of quality of care, and may not be as effective as periodic monitoring of quality indicators at stimulating improvement projects in treatment facilities [23,24]. On the other hand, enrolment of every patient on dialysis, as opposed to a sample, ensured that even the smallest units felt themselves to be partners of the project, and avoided opportunities for patient selection bias. Nevertheless, facility-level results based on small numbers of observations are imprecise, e.g. if eight out of 10 patients meet the quality criterion, the exact confidence interval on the adequacy proportion is 4397%, if 24 of 30 patients meet the criterion, the interval shrinks to 6192%, and if 80 of 100 do, the interval is 7187%. This lack of precision limits the utility of the feedback given to individual centres. Implementation of guidelines provided only 2 months prior to the study may have been difficult for some dialysis facilities. Finally, the usefulness of evaluation of quality of care is markedly reduced if it is not followed by a continuous quality improvement programme within dialysis facilities [25]. This would necessitate implementation of an educational programme across the public and private dialysis treatment sectors, demonstrating providers strong commitment to evidence-based guidelines and enhancing their capacity to measure quality of care and to act on observed deficiencies [25]. A randomized controlled trial has shown that an intervention focused on dialysis adequacy and tailored to overcome specific barriers, such as shortened treatment time, use of catheters and insufficient prescribed dialysis dose, can be successful over a 6 month period [26].
In conclusion, we described substantial variations in six quality indicators among dialysis facilities of western Switzerland. We could not attribute these variations to discordant treatment policies, nor to differences in patient case mix. Better standardization and repeated evaluation of treatment goals and processes, according to recognized clinical practice guidelines, with the help of a national registry for dialysis patients, would be likely to reduce the variability we observed, and potentially improve the quality of care.
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Acknowledgments |
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The Western Switzerland Dialysis Study Group comprised the following. Fribourg: Dr G. Fellay and E. Descombes, Hôpital Cantonal Fribourg. Geneva: Professor P. Y. Martin, Hôpitaux Universitaires de Genève, Dr M. Levy, Hôpital de la Tour and Dr H. Freudiger, Centre dOnex. Jura: Dr M. Brunisholz, Hôpital Porrentruy. Neuchâtel: Dr D. Robert, Hôpital de la Providence and Dr M. Giovanini, Hôpital La Chaux-de-Fonds. Valais: Dr P.-Y. Uldry, Hôpital de Martigny, Dr G. Vogel, Hôpital de Monthey, Dr B. Haldimann, Hôpital de Sierre, Dr E.Blanc, Hôpital de Sion, Dr P. Evequoz Regionalspital Visp, Dr M. Schmid Regionalspital Brig. Vaud: Dr P. Scherrer, Hôpital de Château dOex, Professor J. P. Wauters (study director, present address: University Hospital, Bern, Switzerland), CHUV Lausanne, Professor J. P. Guignard, Division de Néphrologie Pédiatrique, CHUV Lausanne, Dr B. von Albertini, Clinique Cécil, Lausanne, M.-T. Hudry, Centre de Dialyse de Nyon, Dr T. Gautier, Hôpital des Samaritains, Vevey, Dr G. Halabi, Hôpital de zone, Yverdon. Bern: Dr Z. Glueck, Regionalspital Biel, Bern.
Conflict of interest statement. None declared.
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Notes |
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References |
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