1University Hospital Lausanne (CHUV), Lausanne, 2University Hospital Geneva (HUG), Geneva, Switzerland and 3University of Pennsylvania Medical Center, Philadelphia, PA, USA
Correspondence and offprint requests to: Jean-Blaise Wasserfallen, MD MPP, Medical Direction, Rue du Bugnon, 46, CH-1011 Lausanne, Switzerland. Email: jwasserf{at}chuv.hospvd.ch
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Abstract |
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Methods. All chronic HD and PD patients in the 19 centres of western Switzerland were requested to fill in the validated Euroqol-5D® generic QOL questionnaire, assessing health status in five dimensions and on a visual analogue scale, allowing computation of a predicted QOL value, to be compared with the value measured on the visual analogue scale.
Results. Of the 558 questionnaires distributed to chronic HD patients, 455 were returned (response rate 82%). Fifty of 64 PD patients (78%) returned the questionnaire. The two groups were similar in age, gender and duration of dialysis treatment. Mean QOL was rated at 60±18% for HD and 61±19% for PD, for a mean predicted QOL value of 62±30 and 58±32% respectively. Results of the five dimensions were similar in both groups, except for a greater restriction in usual activities for PD patients (P = 0.007). The highest scores were recorded for self-care, with 71% HD and 74% PD patients reporting no limitation, and the lowest scores for usual activities, with 14% HD and 23% PD patients reporting severe limitation. Experiencing pain/discomfort (for HD and PD) or anxiety/depression (for PD) had the highest impact on QOL.
Conclusions. QOL was equally diminished in HD and PD patients. The questionnaire was well accepted and performed well. Improvement could be achievable in both groups if pain/discomfort and anxiety/depression could be more effectively treated.
Keywords: chronic renal failure; haemodialysis; peritoneal dialysis; quality of life
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Introduction |
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Many different generic and disease-specific questionnaires or interview techniques have been used for assessing the QOL of patients with advanced kidney disease [2]. Overall, studies have shown that global QOL is severely impaired. Results were not always consistent, because they were used at different stages of the disease and in different settings. Comparisons of QOL between haemodialysis (HD) and peritoneal dialysis (PD) have also been performed at different stages of the disease and in different settings. Results were not always consistent in the first place because many different instruments were used: the generic SF-36 questionnaire [37], the quality index score developed by Spitzer [8], the generic EORTC-30 questionnaire [9], or specific instruments such as the KDQOL-SF [6], or the CHOICE instrument [7]. All these instruments give multidimensional results, have few dimensions in common and do not allow comparison between them, nor a simple interpretation, or a linkage with economic assessments.
So far, only two studies used the EuroQol-5D® (EQ-5D) generic questionnaire. One of them compared it with the SF-36 [3] and the other used it along with two other patient preference measurement tools, the time trade-off and the standard gamble [10]. Despite its infrequent use, the EQ-5D instrument has many advantages: it is very easy to use, has been translated and validated in many languages, and its five questions and visual analogue scale impose a minimal burden on patients. In addition, it allows comparisons of QOL as measured in individual patients with predicted values derived from a sample general population, thus confronting two different perspectives for the same health states. Finally, the global score is a numeric figure that can be used as a utility measure and incorporated into economic evaluations. The primary aims of this study were to assess predicted and measured QOL values, and performance of the EQ-5D instrument in chronic HD and PD patients in the 19 dialysis centres of western Switzerland.
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Subjects and methods |
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Eligible subjects were all dialysis patients treated in these centres, as part of a study assessing quality of care in chronic dialysis. Each patient was asked to complete the EQ-5D generic QOL questionnaire. The EQ-5D was developed by the international EuroQol group as a standardized generic measure for description of health status [11]. This questionnaire is self-administered and composed of five items addressing: mobility (problem in walking about), self-care (problem with washing or dressing self), usual activities (problem with performing usual activities), pain/discomfort and anxiety/depression. Each item offers three response categories including no problem, some problems and extreme problems. In addition, the EQ-5D asks the patient whether his/her health status has improved, has been stable or has deteriorated over the last 12 months. Finally, each patient is requested to evaluate his/her own overall health on a visual analogue scale (EQ-VAS, or thermometer scale) ranging from 0 (worst imaginable health state) to 100 (best imaginable health state), leading to a measured QOL score.
The combination of the three different levels of responses recorded for each of the five items defines 243 possible health states (35 possible combinations). Administration of the EQ-5D to a sample of the general population allowed defining a value for each of these health states (health utility). These values are provided with the instrument [12] and are used as a weight for computing a predicted QOL value, reflecting the preference of the general population for these health states. Measured scores on the visual analogue scale can then be compared with the predicted scores. At the beginning of the questionnaire, data about age, gender and duration of dialysis treatment were requested, but the patient was not obliged to provide his/her name, although space was left to do so.
Questionnaires were distributed by the nursing staff and the patients were asked to respond to the questions at home and return the questionnaire to the dialysis centre, if preferred anonymously, by dropping them into a drop box. When patients had trouble reading, writing or understanding the questionnaires, a dedicated nurse could provide assistance. No recall procedure was carried out to increase the response rate.
Results were analysed by dialysis treatment modality and by centre. Analysis was repeated after restricting HD data to the centres that also offered PD. Further analysis compared the results by centre size (number of patients <25 or not), by response rate (<90% or not), by teaching status and by type of financing (public vs private). Categorical variables were compared with the 2 test and continuous variables with MannWhitney U-tests or Student's t-tests, as appropriate. The relationship between the five items and the measured QOL was assessed by linear regression, as were the relationships with age, duration of treatment and health state over the prior 12 months.
Quality performance of the questionnaire was assessed as response rate to the different items and to the scale, and distribution of responses over the different responses categories.
Differences between measured and predicted QOL were computed for each patient and means were computed for each dialysis modality and centre. Differences in QOL and differences between measured and predicted QOL by evolution of health state were compared with a two-way ANOVA. Statistical significance was assumed for P values <0.05.
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Results |
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Of the 558 questionnaires distributed to chronic HD patients, 455 were returned (response rate 82%). The centre-specific response rate ranged from 55.6 to 100%, with a median of 92.9%. For PD patients, 50 of the 64 questionnaires were returned (response rate 78%). The centre-specific response rate ranged from 50 to 100%, with a median of 90%. Responders used the help of dialysis nurses to complete the questionnaire only in a few cases. Almost all patients (98%) were Caucasians. HD and PD patients were not statistically different in age (64±15 vs 60±17 years), gender (male gender 63 vs 55%) and duration of dialysis treatment (4.0±4.5 vs 3.2±4.9 years). Only 7.5% of HD and 8% of PD patients had started dialysis in the year of the study, and their health status assessment was not different from the other patients. Responders were also similar to the whole dialysis population treated in the different dialysis centres, and no differences were observed between the different centres. The corresponding values when analysis was repeated by centre size (> or <25 patients), response rate (> or <90%), teaching status (teaching or not) and type of financing (public or private) are displayed in Table 1. Only three statistically significant differences were observed, for which no obvious explanation exists: centres offering both HD and PD had more male patients; PD centres with high response rates were younger; and PD patients in teaching hospitals had been on dialysis for a longer time.
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Altogether, there was no statistically significant difference in response distribution between the 19 different HD centres or the nine PD centres, nor when analysis was restricted to HD centres offering PD. When analysis was repeated by centre size, response rate, teaching status or type of financing, only two statistically significant differences were observed: HD patients in centres with low response rate reported more pain/discomfort than HD patients in centres with high response rates (P = 0.007); and HD patients in larger centres reported more anxiety/discomfort than HD patients in smaller centres (P = 0.032).
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Discussion |
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The EQ-5D instrument measures health states along five components reflecting physical, functional and mental dimensions. Altogether, these five dimensions explained a third and half of the observed variance in QOL in HD and PD patients, respectively. Four of these five dimensions were statistically significant in HD patients, and two of them in PD patients. Interestingly, the dimensions associated with the highest variation in QOL dealt with pain/discomfort and anxiety/depression in both treatment modalities. The prevalence of depression in our population of dialysis patients was similar to the one described in prior studies [1]. Although substantial individual variation exist, as reflected by the wide 95% confidence interval, this finding is of particular interest and should attract the attention of physicians because a specific treatment is available. If successful, it would, on average, improve QOL of these patients by 1020%. This finding might also explain why a study using the index score of Spitzer [8] found that variance in responses was not explained by case-mix variations only, which usually do not include these variables. Thus, pain/discomfort and anxiety/depression might deserve special attention, because they are not always part of routine clinical assessment.
PD is often presented as the easier and less cumbersome dialysis modality, but is used for a minority of patients. Even if the majority of our PD patients performed automated PD, our results showed that they reported a severe impairment in their usual activities, which was greater than the one described by HD patients. This surprising factor should be kept in mind when information about dialysis modalities is presented to patients with ESRF.
Another interesting finding was that no major difference was recorded between the different dialysis centres, in measured or predicted QOL, or even in the differences between these two measures. This result is not consistent with the findings by Mozes et al. [8], who noted differences between dialysis centres, which were not explained by differences in case-mix only. The small size of our centres might explain these discrepant results.
Although mean measured and predicted values were similar for the whole population, individual correlation between them was low (r = 0.197). This finding has already been described when the EQ-5D was used in other settings, such as chronic disorders (rheumatoid arthritis, osteoarthritis of the knee) or intensive care stays, or acute conditions such as AIDS. Several explanations have been proposed: first, different raters assign different values to the same health state, and consequently have different preferences for these health states [13]; secondly, the predicted values are derived from studies on the general population, whereas the values measured on thermometer scale reflect the opinion of the patient. If they suffer from chronic diseases, they are likely to alter their expectations and goals to cope with their limitations [14]. This might explain why results on patients with chronic diseases are consistent between them and not with those observed on survivors of intensive care hospitalization. Finally, the EQ-5D dimensions are recorded on a three-point scale, which might force responses to the mid-range category, as few patients endorse the severe value, and some limitation is often present, which diverts the answer away from the no limitation value [15]. A comparison of the EQ-5D thermometer scale results with those obtained on a five-point rating scale showed results consistent with this hypothesis [16]. On the other hand, such a limitation of the EQ-5D instrument can be viewed as an advantage in itself, as it allows deriving preferences of both the patients and the general population at the same time, and thus offers the two most useful perspectives to incorporate into other studies assessing the impact of diagnostic or therapeutic procedures, such as economic analysis for example.
Our study has also limitations. First, its cross-sectional design precludes comparison with QOL before dialysis, which has been shown to have an important impact [35]. Secondly, as it was designed to be anonymous, no systematic link could be made with a case-mix variable or with adequacy of dialysis [17], which was found to have an impact on physical and emotional dimensions in a study using the SF-36 questionnaire or on satisfaction with care [18]. Thirdly, any comparison between HD and PD should be made with caution, because we did not exclude therapy selection, or differences in QOL before dialysis [3]. Therefore, our findings of a similar decrease in QOL within the two groups should be put in perspective with the findings of other studies using the SF-36 questionnaire. Merkus et al. showed a favourable effect on physical QOL over time in HD patients, as compared with PD patients [4], whereas Diaz-Buxo et al. described no difference in HD patients in this dimension, but a higher score for mental processes in PD patients, after adjustment for laboratory tests results [5].
Further studies should assess how the EQ-5D compares with other generic or disease-specific instruments such as the SF-36 or the KD-QOL [6], or be used as a predictor of poor outcomes [19], mortality and hospitalization [20], as was shown for the SF-36 questionnaire.
In conclusion, the EQ-5D appeared to be a promising surveillance instrument for HD and PD patients. It showed that ESRF patients experience low levels of QOL with both dialysis modalities, but that some characteristics could be better targeted to improve their QOL. In addition, the very high response rate observed in this study was encouraging: it indicated that patients were willing to participate in this kind of survey. As a consequence, EQ-5D could be used more frequently by other dialysis centres in our country or abroad, as it is simpler to administer compared with the more widely used SF-36 questionnaire, and can be linked with other kinds of studies, including economic analyses.
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Participating nephrologists |
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Acknowledgments |
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Conflict of interest statement. None declared.
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References |
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