Quality of life in patients with chronic kidney disease: a cross-sectional study comparing patients on hemodialysis, peritoneal dialysis and with kidney transplantation.

Aims: The methods of renal replacement therapy influence highly the quality of life (QOL) of patients with chronic kidney disease. The present study aimed to evaluate and compare the QOL in patients undergoing hemodialysis (HD), peritoneal dialysis (PD) and kidney transplantation (KT). Methodology: The sample consisted of 186 patients attending Nicosia General Hospital in 2012, 118 HD patients, 23 PD patients and 45 KT patients. QOL was assessed by the Greek Kidney Disease Quality of Life-Short Form (KDQOL-SF 36). Results: Patients on HD had worse scores in all components. All three patient groups showed Original Research Article Tomazou et al.; BJMMR, 8(6): 516-525, 2015; Article no.BJMMR.2015.474 517 highest scores in mental health (HD: 57.7; PD: 70.3; KT: 75.6), whereas the lowest scores were observed in the component role physical (HD 33.1; PD 54.4 and KT 56.7) and general health (HD 32.5; PD 44.1 and KT 60.4). KT patients achieved highest scores in the physical component summary and mental component summary, as well as in the component summary of renal disease, followed by peritoneal dialysis patients. Male gender was significantly associated with higher score. Conclusion: The study demonstrate that among the three groups the patients on hemodialysis had the worst scores, whereas the best scores are seen in KT patients. Lower scores are reported in the physical health component and here especially in the general health. Physicians as well as nursing personnel should be aware of the effects of dialysis and could improve both physical and mental health implementing empowerment programs in departments of HD and PD, to support patients in managing their health-related conditions.


INTRODUCTION
The number of patients with chronic kidney disease (CKD) is growing rapidly around the world. The methods currently applied globally and in our country as replacement therapy of renal function is the hemodialysis (HD) through an artificial kidney, the peritoneal dialysis (PD) and kidney transplantation (KT) from living or cadaveric donor. Consequently, there is increasing scientific interest from health professionals about the impact of support methods of renal function in quality of life (QOL) of patients with CKD.
The term QOL refers to the physical, psychological and social domains of health seen as distinct areas that are influencing patients experiences, beliefs, expectations and perceptions. The WHO defines QOL as "an individual's perception of their position in life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards and concerns" [1].
The purpose of this study was to investigate the specific determinants that affect the assessment of health-related QOL of patients undergoing alternative renal replacement. Specifically, the investigation focuses on the comparison between patients undergoing hemodialysis, peritoneal dialysis and patients who underwent successful kidney transplantation according to the patient's subjective perception.

Study Design and Study Population
The present study was carried out in the department of nephrology of the General Hospital of Nicosia in Cyprus. A cross-sectional study was employed, to enable comparisons between different patient groups with chronic kidney disease.
Between May 2012 and October 2012 all patients with end stage of renal disease (ESRD) undergoing renal replacement therapy with HD, PD or KT were consecutively included.
Inclusion criteria for patients to be eligible for the study were: age 18 years and older, both sex, diagnosis of ESRD, renal replacement therapy with HD, PD or KT for at least 6 months prior to the study, Greek as native language, adequate level of cooperation, perception and comprehension, voluntarily participation after signing the consent form.
A total of 186 patients agreed to participate who met the criteria. Of them 118 (63.4%) were undergoing chronic maintenance HD for four hours three times per week in the hemodialysis unit in the General Hospital in Nicosia, 23 (12.4%) were undergoing PD and 45 (24.2%) had undergone KT.
An ethical approval for the study was obtained from the Ethics Committee of the Health Ministry of Cyprus.

Data Collection and Instruments
Data were collected by a self-administered questionnaire which was distributed to all patients. HD patients completed it with the help of the researcher-nurse during the HD session. The PD and KT patients received the questionnaire at one of their scheduled appointment and were requested to complete it during the consultation waiting time. The researcher-nurse was available to provide explanations and to assist patients who were not able to read and write.
The first section of the questionnaire included demographic and clinical information, i.e. sex, age, marital status, cause of renal disease and duration of renal replacement therapy. The second section obtained a health-related quality of life (HRQOL) instrument, namely the Kidney Disease Quality of Life Short-Form (KDQOL-SF 1.3) [2], which has been used in several settings with ESRD patients [3][4][5].
The Greek version of KDQOL-SF 1.3 which is used in the present study was validated by Malindretos [6]. This instrument for quality of life assessment combines a disease-specific instrument (KDQOL) with a generic instrument, the 36-item Short Form health survey (SF-36). The latter is designed to measure eight different areas of health, including physical functioning, bodily pain, role limitations due to physical health problems as well as due to personal or emotional problems, emotional well-being, social functioning, vitality and general health perceptions. It also provides two summary measures, which refer to the physical health component (PHC) and the mental health component (MHC) scores.
KDQOL-SF 1.3 includes additionally to the SF-36 scales further specific dimensions of chronic kidney disease. In the Greek version are included 49 items that can be summarized in 12 subscales: Symptoms/problems, effects of kidney disease, burden of kidney disease, work status, cognitive function, quality of social interaction, sexual function, sleep, social support, dialysis staff encouragement, overall health and patient satisfaction.
Items from each concept in both instruments are summed and rescaled with a standard range of 0 to 100, where 100 represent the best health related quality of life.

Statistical Analysis
All analyses were performed using the program Statistical Package of Social Sciences (SPSS 20). The quantitative variables were described as means and standard deviations (SD) for continuous variables and as frequencies and proportions for categorical variables.
Pearson's r was applied to test for correlations among study variables. Kolmogorov-Smirnov test was applied to test if the quantitative variables of the sample followed normal distribution. If the sample does not follow normal distribution, nonparametric tests were applied. The Mann-Whitney test was used for comparisons of ranked scores among two groups and the table ANOVA or Kruskal-Wallis for the three groups, as appropriate.     Table 3.

Descriptive Analysis of the KDQOL Scale
Furthermore we examined whether age and sex were associated with HRQOL. Since age did not follow a normal distribution non-parametric tests were applied after recoding the variable into three age groups (<50 years, 50-65 years, >65 years). Kruskal-Wallis test was applied to evaluate the associations among the three agegroups (Table 4).
With regard to age, younger patients (<50 years) on hemodialysis show higher scores in the scales role physical and mental health, as well as in burden of kidney disease and sexual function, whereas in the dimension effects of kidney disease patients aged >65 years show significant higher scores. In patients on peritoneal dialysis only the parameter dialysis staff encouragement appears to be associated with younger (<50 years) and older (>65 years) age. Younger patients with kidney replacement show significantly higher scores in cognitive function and sexual function. For more details refer to Table 4 and Table 5.
For the comparison between males and females, Mann-Whitney U test was applied for all three patient-groups (Tables 6 and 7 No statistical significant differences were observed between male and female kidney transplant recipients. For more details refer to Table 6 and Table 7.      [5]. Several studies have already compared the QOL of dialysis patients with the general population, the majority disclosing the negative impact of CKD and its treatments [5,6]. The present study, even with the limitation of being an observational cross-sectional study with a small number of patients [7], was conducted to evaluate the HRQOL in three groups of patients with CKD, different characteristics (age, gender, duration of illness) and under different renal replacement treatments (HD; PD and KT).
The results demonstrate that HD patients had the worst scores, whereas the best scores are reported in KT patients. In all three groups, lower scores are reported in the physical health component and here especially in the general health. In other chronic diseases than CKD, a greater impact in mental health comparing to physical health was found. This situation can be explained by the higher average age. Similar results are found in other studies [8,5].
Comparisons of QOL between hemodialysis and peritoneal dialysis patients are not consensual. In our study, the PD group achieved better scores in scales like "Effects of kidney disease", "Burden of kidney disease" and "Patient satisfaction". According to the literature peritoneal dialysis patients select this dialysis technique to keep their active lives and possibility to study or work [9,10]. Though in the present study the most patients are retired, they are all the same more active, more autonomous and motivated than the HD patients.
On the other hand, our hemodialysis patients are integrated in a Hospital Unit that selects older, sicker and more dependent persons [11]. These facts may be a partial explanation for the better results of our PD patients. Individual characteristics of personality are obviously not evaluated in our study, but must also be considered when analyzing these results. Apart from these, hemoglobin levels, creatinine, adequacy of dialysis and comorbidity are important parameters for the HRQOL.
Female gender and older age emerged as predictors of lower HRQOL score. Our findings are in agreement with other studies, where lower scores are reported in women and in higher ages [12][13][14][15]. The reason for the lower scores in females may be psychological, since female patients show generally more depression and anxiety which is associated with lower QOL and has been well documented in various studies [16,17].
There are some limitations to this study. First, the patients were recruited from a single department, which may limit the generalizability of the findings. Second, the study was conducted among three groups of CKD patients with no even distribution according to age. Due to the limited sample size, this could suggest the existence of bias, as the younger patients tended to report a higher HRQOL. Third, we did not investigate the impact of clinical factors, such as the adequacy of hemodialysis or peritoneal dialysis, levels of hemoglobin or creatinine or comorbidities on the QOL of these patients. There are many other factors that contribute to the QOL, limiting thus the comparability at the baseline.

CONCLUSION
In conclusion, HD patients in our study had the lowest scores comparing to peritoneal dialysis patients or even to kidney transplant recipients, which is in accordance with other studies [18][19][20].
The worst scores in all three groups were found in the Physical Health Component, whilst the highest being observed in dialysis staff encouragement and quality of social interactions. Variables found to be related with QOL were age and gender, whereas males and younger patients show significant higher values [21].
The study has further demonstrated the feasibility of using a standardized quality of life instrument in different groups of CKD patients and comparing the results among them. Renal nurses should participate actively in investigating and improving the health-related quality of life, mainly for people receiving hemodialysis. Assessing QOL in these patients could give nurses additional insight how they adapt to their chronic illness, in terms of physical, psychological and social process. The attention of all health professionals to the patient's subjective perception about their health can be determinant in achieving the best medical intervention and improving survival.

CONSENT
All authors declare that written informed consent was obtained from the patient (or other approved parties) for publication of this original research.

ETHICAL APPROVAL
All authors hereby declare that the study design and realisation of the study have been examined and approved by the appropriate ethics committee and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki.