Translation and cross-cultural adaptation of the Kidney Transplant Questionnaire 25 to Greek

Abstract

BACKGROUND

Kidney transplantation leads to continuous improvement in the survival rates of kidney transplant recipients (KTRs) and has been established as the treatment of choice for patients with end-stage kidney disease. Health-related quality of life (HRQoL) has become an important outcome measure. It is highly important to develop reliable methods to evaluate HRQoL with disease-specific questionnaires.

AIM

To translate the disease-specific instrument Kidney Transplant Questionnaire 25 (KTQ-25) to the Greek language and perform a cross-cultural adaptation.

METHODS

The translation and adaptation of the original English version of the KTQ-25 to the Greek language were performed based on the International Quality of Life Assessment.

RESULTS

Eighty-four KTRs (59 males; mean age 53.5 ± 10.7 years; mean estimated glomerular filtration rate 47.7 ± 15.1 mL/min/1.73 m²; mean transplant vintage 100.5 ± 83.2 months) completed the Greek version of the KTQ-25 and the 36-item Short-Form Health Survey, and the results were used to evaluate the reliability of the Greek KTQ-25. The Cronbach alpha coefficients for all the KTQ-25 dimensions were satisfactory (physical symptoms = 0.639, fatigue = 0.856, uncertainty/fear = 0.661, appearance = 0.593, emotions = 0.718, total score = 0.708). The statistically significant correlation coefficients among the KTQ-25 dimensions ranged from 0.226 to 0.644. The correlation coefficients of the KTQ-25 dimensions with the SF-36 physical component summary (PCS) ranged from 0.196 to 0.550; the correlation coefficients of the KTQ-25 with the SF-36 mental component summary (MCS) ranged from 0.260 to 0.655; and the correlation coefficients of the KTQ-25 with the total scores with the SF-36 PCS and MCS were 0.455 and 0.613, respectively.

CONCLUSION

According to the findings, the Greek version of the KTQ-25 is valid and reliable for administration among kidney transplant patients in Greece.

Key Words: Kidney Transplant Questionnaire 25, Kidney transplantation, Kidney transplant recipients, Health-related quality of life, Quality of life

Core Tip: The Kidney Transplant Questionnaire 25 (KTQ-25) is a disease-specific instrument that is used to evaluate the health-related quality of life of patients who suffer from end-stage kidney disease and who have undergone kidney transplantation. Prior to this study, there was no disease-specific instrument for these patients in our country. We translated the KTQ-25 into Greek according to the International Quality of Life Assessment. The translated version of the KTQ-25 was administered to a Greek cohort of kidney transplant recipients. Scores of the five dimensions of the KTQ-25 were calculated, and statistical tests were performed to estimate the reliability and validity of the translated scale.

INTRODUCTION

There is an increasing amount of interest in the evaluation of health-related quality of life (HRQoL), especially among patients suffering from chronic diseases. The importance of evaluating HRQoL should not be underestimated because this process it plays an essential role in determining the efficacy of medical interventions, improving the process of making clinical decisions, and evaluating the quality of health care[1]. Moreover, the assessment of patients’ perceptions of their health status is especially important for the evaluation of chronic disease outcomes. These perceptions are important for health care professionals to understand disease complications among patients and the effects of treatment on their health status. Based on this information, treatment adjustment should be considered to improve the management and progression of patients[2,3].

Kidney transplant recipients (KTRs) are a special category of patients suffering from chronic disease. Kidney transplantation is widely available and remains the gold standard treatment for patients with end-stage kidney disease receiving renal replacement therapy, hemodialysis, or peritoneal dialysis[4]. Compared with dialysis, kidney transplantation ensures improved patient outcomes, including cardiovascular and total survival as well as QoL[5]. The ability to evaluate HRQoL among KTRs is critical not only for optimizing the care of an individual patient but also for assessing the effectiveness of various treatment strategies and guiding future improvements in health care among specific populations. The estimation of HRQoL among KTRs requires the use of an instrument that is able to achieve both comprehensive and disease-specific assessments, considering that patients are maintained on chronic immunosuppressive therapy after kidney transplantation[6,7].

Most experts in the field of HRQoL evaluation recommend the use of two kinds of questionnaires when the target group concerns patients with chronic diseases. One disease-specific instrument was designed especially for the disease of interest, and one generic instrument was used[8,9]. The generic questionnaire enables comparisons of the studied patient group with the general population and with other patient groups; the disease-specific questionnaire is more accurate for estimating longitudinally changes in HRQoL, especially changes related to specific therapeutic interventions[2,8,10].

In Greece, there are no translated and adjusted disease-specific questionnaires for the estimation of HRQoL among KTRs. Thus, this study aimed to translate the “Kidney Transplant Questionnaire 25 (KTQ-25)” to Greek and to subsequently assess its reliability and validity in this patient population[11]. A Greek version of such a questionnaire is highly necessary considering the growing number of KTRs in Greece. Furthermore, a national transplant project has been initiated with the aim of increasing organ donation and the number of kidney transplantations over the next few years.

MATERIALS AND METHODS

Study population and data collection

This was an observational, prospective, single-center study conducted at the Kidney Transplant Unit of the University Hospital of Ioannina. The study population included 84 KTRs who were recruited during their routine follow-up visit at the outpatient clinic of the Kidney Transplantation Unit of our hospital. All patients signed an informed consent form after being informed in detail about the study. The inclusion criteria were adults (age ≥ 18 years), a well-functioning kidney graft for ≥ 12 months, stable clinical condition during the last month, and good knowledge of the Greek language. The exclusion criteria were active malignancy, chronic severe liver or infectious disease, recent (< 1 month) hospitalization for bacterial or viral infection, acute rejection, cardiovascular event and bone fraction, and scheduled switch to dialysis due to failing graft in the next 3 months. The study protocol was approved by the Ethics Committee of the University Hospital of Ioannina.

At enrollment, social-demographic and anthropometric data along with medical history details were collected from the patients’ medical files. Complete hematological and biochemical laboratory parameters and morning urine analysis tests were performed at study entry. The KTQ-25 was administered via in-person interviews to all KTRs by the same health care professional (registered nurse) to enhance the participants’ understanding of the questions and to minimize missing data. All interviews were conducted in a relaxed and quiet environment to avoid any distractions. The general health-related instrument utilized was the existing Greek version of the SF-36 Health Survey (SF-36)[12]. Each patient completed both questionnaires on the same date and during the interview.

Questionnaires

The original KTQ-25 was developed in 1993 by Laupacis et al[11]. It consists of 25 items grouped in the following 5 dimensions: (1) Physical symptoms (6 items); (2) Fatigue (4 items); (3) Uncertainty/fear (5 items); (4) Appearance (4 items); and (5) Emotions (6 items). The first dimension (physical symptoms) is patient-specific. Each item is scored on a 7-point Likert scale. Higher scores for each item represent better health status and/or fewer health problems associated with the transplant. For the analysis, all scores in each domain were added and divided by the number of items in that dimension.

The SF-36 Health Survey is a generic HRQoL instrument that includes 36 items categorized into 8 dimensions: Physical functioning (10 items), role functioning-physical (4 items), bodily pain (2 items), general health (6 items), vitality (4 items), social functioning (2 items), role functioning-emotional (3 items) and mental health (5 items). Two subscales of the SF-36, i.e., the physical component summary (PCS) and the mental component summary (MCS), estimate the physical and mental conditions of patients, respectively. Previous studies have described the use of the SF-36 among patients with end stage renal disease and KTRs[13,14].

Translation methodology

The authors of the KTQ-25 were contacted to obtain the full English version of the KTQ-25 and to obtain permission for the translation. The Greek version of the KTQ-25 was developed according to the cross-cultural adaptation guidelines of the International Quality of Life Assessment translation methodology[15]. The process of developing the Greek KTQ-25 was as follows: Initially, two native Greek speakers with a good level of English language knowledge independently translated the original English version to Greek. Then, a group of health care experts, including a nephrologist, a psychologist, and renal care nurses, revised the two separate translations and developed one common final provisional translation (forward translation). Subsequently, the provisional translation was translated to its original English language by two native English speaker experts (backward translation). Subsequently, the two questionnaires were checked for differences by the expert group, and corrections were made where deemed necessary. The provisional Greek-translated questionnaire was first tested on a pilot basis in a group of 10 KTRs. At the end of the interview, the KTRs were asked about their opinions about the KTQ-25, and all reported that they had no problems completing it or difficulties understanding its content. Consequently, the expert group decided that the translated Greek version of the KTQ-25 was suitable for a larger sample of patients.

Statistical analysis

The KTQ-25 scores are expressed as the means and standard deviations. The reliability of the ΚΤQ-25 was assessed by estimating Cronbach’s alpha coefficient. The construct validity was examined by calculating the Pearson correlation coefficients between the KTQ-25 dimensions, and the concept validity was based on the Pearson correlation coefficients between the scores of the KTQ-25 dimensions and the scores of the two component summaries of the SF-36 (PCS and MCS). Items with a correlation coefficient of 0.4 or more with their own hypothesized scale were accepted[16]. All the collected variables were entered into a database, and a statistical analysis was carried out with the SPSS v26.0 statistical package. Significance was set at 0.05 in all cases.

RESULTS

Overall characteristics of patients

A total of 84 KTRs were included in the study, and the majority of participants were male (59, 70.2%). The mean age was 53.5 ± 10.7 years, and the mean transplant duration was 100.5 ± 83.2 months. Regarding kidney graft donor type, 59.5% of KTRs (n = 50) received a deceased donor graft, 39.3% of KTRs (n = 33) received a living donor graft, and one KTR was transplanted twice. The mean time on the deceased donor transplant list was 53.5 ± 39.7 months. At study initiation, the mean estimated glomerular filtration rate was 47.7 ± 15.1 mL/min/1.73 m² and the mean serum creatinine level was 1.6 ± 0.5 mg/dL.

KTQ-25

The mean time required to complete the KTQ-25 was approximately 13 min, and none of the patients reported any problems understanding and/or completing the questionnaire. The highest score on the KTQ-25 was found for the appearance dimension (6.31 ± 0.94), while the lowest score was found for the physical symptoms dimension (3.98 ± 1.60). The mean scores of the other dimensions were 5.30 ± 1.36 for fatigue, 5.16 ± 1.33 for uncertainty/fear, and 5.03 ± 1.07 for emotions, whereas the total score of the KTQ-25 was 5.20 ± 0.87 (Table 1).

Table 1 Kidney Transplant Questionnaire 25 scores (n = 84).

KTQ-25 dimensions	Mean	SD
Physical symptoms	3.98	1.60
Fatigue	5.30	1.36
Uncertainty/fear	5.16	1.33
Appearance	6.31	0.94
Emotion	5.03	1.07
Total score	5.20	0.87

KTQ-25: Kidney Transplant Questionnaire 25.

The Pearson correlation coefficients for the KTQ-25 dimensions, which were used to evaluate construct validity, are presented in Table 2. The statistically significant correlation coefficients ranged between a minimum of 0.226 for the “Uncertainty/Fear” and “Physical Symptoms” dimensions and a maximum of 0.644 for the “Emotion” and “Uncertainty/Fear” dimensions.

Table 2 Correlation coefficients among Kidney Transplant Questionnaire 25 dimensions.

		Physical symptoms	Fatigue	Uncertainty/fear	Appearance	Emotion
Physical symptoms	Pearson correlation		0.354b	0.226a	0.187	0.395c
Fatigue	Pearson correlation			0.487c	0.182	0.584c
Uncertainty/fear	Pearson correlation				0.073	0.644c
Appearance	Pearson correlation					0.193

^aP < 0.05.

^bP < 0.01.

^cP < 0.001.

The results of the concept validity test, measured by the correlation coefficients between the KTQ-25 dimensions and the component summaries of the SF-36 Health Survey dimensions, are presented in Table 3. The coefficients for the dimensions of the SF-36 were positive in all cases. The correlation coefficients between the KTQ-25 dimensions and the MCS score ranged from 0.260 for the “physical symptom” dimension to 0.655 for the “emotion” dimension. Concerning the PCS score, the coefficients ranged between 0.196 for the “appearance” dimension and 0.550 for the “fatigue” dimension.

Table 3 Correlation coefficients among Kidney Transplant Questionnaire 25 dimensions and SF-36 (n = 84).

KTQ-25 dimensions	PCS	MCS
Physical symptoms	0.143	0.260a
Fatigue	0.550a	0.528a
Uncertainty/fear	0.304a	0.605a
Appearance	0.196a	0.023
Emotion	0.278	0.655a
Total Score	0.455	0.613a

^aP < 0.05.

KTQ-25: Kidney Transplant Questionnaire 25; MCS: Mental component summary; PCS: Physical component summary.

Reliability was measured by Cronbach’s alpha coefficient, which was found to be greater than 0.7 for two dimensions (fatigue and emotion) and less than 0.7 for the other three dimensions (physical symptoms, uncertainty/fear, and appearance). The reliability of the total KTQ-25 score was found to be 0.708, ensuring the required acceptable level. A correlation coefficient of r > 0.70 is considered to indicate an acceptable level of reliability. However, there are references in the literature that even values smaller than 0.7 may be acceptable, especially if the sample, as in our case, is relatively small, while other researchers argue that for the initial stages of a study, a Cronbach alpha coefficient between 0.5 and 0.6 is sufficient[17,18]. The calculated values of Cronbach’s coefficient α for each dimension of the Greek version of the KTQ-25 are listed in Table 4.

Table 4 Cronbach’s alpha coefficient (n = 84).

KTQ-25 dimensions	Cronbach’s alpha	Items
Physical symptoms	0.639	6
Fatigue	0.856	5
Uncertainty/fear	0.661	4
Appearance	0.593	4
Emotion	0.718	6
Total Score	0.708	25

KTQ-25: Kidney Transplant Questionnaire 25.

DISCUSSION

The Greek version of the KTQ-25 is the first disease-specific instrument for the evaluation of the HRQοL in KTRs that has been translated into the Greek language and validated in a cohort of stable kidney transplanted adults. According to our study results, the Greek version of the KTQ-25 is valid and reliable for administration in Greek KTRs.

The sample size of other studies evaluating the psychometric properties of specific disease instruments, as in our study, can never reach the sample number that is used for the validation of generic instruments due to the shortage of available patients with a certain disease. The validation study of the original version of the KTQ-25 included only 26 KTRs, whereas the Spanish validation study included only 31 participants[2,11]. Notably, a total of 84 KTRs agreed to participate in the present study, a sample size far exceeding those of previously published studies.

We considered that it would be optimal to apply the questionnaires by the method of in-person interviews (conducted by the same person) to minimize the number of items that would left incomplete. As the mean duration required to complete the questionnaire was approximately 13 min, this short time required renders the KTQ-25 a suitable tool for everyday clinical use. Moreover, the KTQ-25 could be utilized as a self-completed questionnaire after providing brief instructions to the patients. In the latter scenario, the time required to complete the questionnaire might be even less.

Most of the correlation coefficients found between the five dimensions of the KTQ-25 were statistically significant, and these were in all cases positive and usually moderately strong, ensuring satisfactory construct validity. Furthermore, all the correlation coefficients found between the dimensions of the KTQ-25 and the two summary components, the PCS and the MCS, of the SF-36 were positive, proving that both instruments evaluated the same concept and ensured the appropriate concept validity of the translated KTQ-25.

The internal consistency reliability of the KTQ-25 and its five dimensions was satisfactory, as Cronbach’s α coefficient for the overall KTQ-25 was 0.708, which was marginally greater than the acceptable limit of 0.7 but not for all of its individual dimensions. The minimum Cronbach α coefficient was 0.593 for the appearance dimension, and the maximum was 0.856 for the fatigue dimension. Cronbach’s α coefficient for the original version of the KTQ-25 was 0.76 for physical symptoms, 0.94 for fatigue, 0.63 for uncertainty/fear, 0.61 for appearance, and 0.80 for emotions[8,11]. Similarly, in the Spanish version by Rebollo et al[2] and the study by Chisholm-Burns et al[19], the lowest Cronbach α coefficients were observed in the appearance dimension (0.69 and 0.62, respectively), and the highest coefficients were observed in the fatigue dimension (0.93 and 0.90, respectively). According to the available literature, if a scale shows a low degree of internal consistency, the clarity of the propositions may need to be reconsidered, or this may be due to the small degree of propositions per dimension[17,18].

CONCLUSION

The findings of our study show that the validity and reliability of the Greek version of the KΤQ-25 are satisfactory. A useful disease-specific instrument for the evaluation of the HRQοL of KTRs is now available in the Greek language. In the future, multicenter studies with larger sample sizes are required to estimate the validity and reliability of the KTQ-25 and to establish the Greek version of the KTQ-25 structure through confirmatory factor analysis. Ideally, future studies should assess the clinical value of using the KTQ-25 to assess HRQoL in everyday practice, thus providing guidance for therapeutic approaches. Furthermore, future studies should examine the significance of the Greek version of the KTQ-25 as a potential predictor of adverse outcomes.

ACKNOWLEDGEMENTS

The authors would like to thank all kidney transplant recipients who agreed to participate in the study.