Objectives: Liver transplant recipients must adapt to a new life after transplant. We report the effects of a support group on physical and psychosocial adaptation of liver transplant recipients.

Materials and Methods: The study used a quasi-experimental design, comparing an intervention group and a control group. Data were collected between January 2011 and May 2012 with 73 liver transplant recipients. A patient identification form, Modified Transplant Symptom Occurrence and Symptom Distress Scale – 58, and SF-36 were used for data collection. The intervention group attended support group meetings, while the control group received a routine follow-up. Data were analyzed with t test and The Repeated Measures ANOVA with 1 between-group factor.

Results: The results indicated that the support group intervention increases physical, psychological, and social adaptation of liver transplant recipients. Specifically, this effect of the support group was accrued after support group intervention and decreased 3 months after intervention.

Conclusions: A support group intervention can have a positive effect on liver transplant recipients’ physical, psychological, and social adaptations.

Key words : Liver transplant, Support group, Quality of life, Symptom

Introduction

Liver transplant is an effective method used to treat end-stage liver disease. Liver transplant recipients (LTRs) experience adaptation after transplant. Many studies have reported that patients may have physical, psychological, and social problems during this period.^1-4 In a meta-analysis⁵ and a systematic review related to quality of life (QOL) after liver transplant,⁶ the effects of QOL interventions were recommended to be carried out after transplant. The literature states that support groups are effective in patients with liver disease.⁷

Background
Support groups allow patients with similar diseases to share their knowledge of, experiences with, and problems associated their disease and lend support to each other.^8,9 Support groups help people gain information to help them adapt to a new social life, and to interact, and share experiences with friends.⁹ It is important for liver transplant patients to adjust to their life after transplant.¹⁰

Support groups have been used with organ transplant patients for a long time,^11,12 and are still being used in present in many transplant centers worldwide. There have been studies on the effects of support groups with specific training topics on organ transplant patients (eg, mindfulness-based stress reduction,^13,14 fitness training groups,¹⁵ physical rehabilitation,¹⁶ and counseling for exercise and diet).¹⁷ These studies have reported that support groups reduce anxiety levels¹⁸ and improve psycho-social adaptation,¹⁹ allow patients to return sooner to work,²⁰ have a positive influence on the self-management, self-efficacy, and health care status,¹⁵ and increase QOL in patients waiting for transp-lant.²¹ Stress reduction intervention has been reported to decrease depression and anxiety and to increase sleep quality and QOL of organ transplant recipients.^13,14 Physical rehabilitation, aimed at decreasing tiredness, has been shown to improve daily life activities, QOL, and autonomy also have been known to reduce anxiety and depression.¹⁶ Studies must be performed on the effectiveness of support groups formed to increase the physical, psychological, and social adaptation of liver transplant recipients.

The aim of this study was to examine the effects of support group intervention on the physical, psychosocial, and social adaptation of liver transplant recipients. The following hypotheses were tested:

H1: Providing a support group intervention will yield a higher adaptation to the physical status caused by the disease than that of the control group.

H2: Providing a support group intervention will yield a higher adaptation level to the psychological status caused by the disease than that of the control group.

H3: Providing a support group intervention will yield a higher level of adaptation to the social status caused by the disease than that of the control group.

Materials and Methods

Design
The study adopted a quasiexperimental design.

Participants
The research was conducted in the liver transplant outpatient clinic of a university hospital in the western part of Turkey. Inclusion criteria were being between the age of 18 and 65 years, a willingness to participate in the study, no record of a psychiatric disease, being a native speaker of Turkish, experiencing their first liver transplant, residing in the city of Izmir (or a city close to Izmir), having the ability to attend a support group, and being at least a primary school graduate. The exclusion criteria included hospitalization, having a liver transplant due to alcoholic liver failure, and multiorgan transplant.

A list of patients fulfilling the inclusion criteria at the university hospital where the study was conducted was made. Patients were informed about the aim of the study, the intervention to be performed, and the collection of data. They were asked whether they would like to be in the interventional or the control group. The attendance ratio of intervention participants was 88%. Assignment of the patients into the study was based on the patients’ decisions and demographic features (Figure 1). The study was approved by the Ethical Review Committee of the Institute. All of the protocols conformed to the ethical guidelines of the 1975 Helsinki Declaration. Written informed consent was obtained from all subjects.

Intervention
Because we wanted there to be the experience of sharing among participants in the use of computer, low, face-to-face support intervention was used. Support group meetings were held in a meeting room located in the liver transplant outpatient clinic. Support group meetings took 2 hours (theoretical knowledge and experience sharing). The study sample was divided into 3 support groups; each support group included 12 to 14 patients, and met 5 times with each group. A total of 15 meetings was held. Because most of the patients agreed to meet monthly, meetings were conducted once a month. The meetings began in September 2011 and were completed in February 2012.

Data collection
Data were collected using a face-to-face interview technique. Information about the study objectives and support group intervention was provided during individual interviews. Patients in the intervention group attended at least 3 support group meetings. Data were collected in 3 stages over 16 months: at baseline, at follow-up No. 1, and follow-up No. 2 LTRs. Follow up-1 data assessment time was 5 months after baseline data collection time for control group, after completion of the support group for intervention group. Follow up-2 date assessment time was 3 months of follow up-1 for both groups. In the baseline stage, data were obtained using the patient identification form, Modified Transplant Symptom Occurrence and Symptom Distress Scale—58—MTSOSD-58, and SF-36 in the first interview in the control group, and before the support group intervention in the intervention group. In the follow up-1 stage, data were collected 5 months after the baseline in the control group, and after completing the support group in the intervention group. In the follow up-2 stage, data were collected 3 months after follow up-1 in the control group and 3 months after completing the support group intervention in the intervention group. In follow up-1 and follow up-2, data were obtained using MTSOSD-58, and SF-36 in both the control group and the intervention group. We gave the booklet that involved information about life after liver transplant to both control and interventional group.

Instruments
To collect the data, patient identification form, knowledge level assessment questionnaire, the Modified Transplant Symptom Occurrence and Symptom Distress Scale—58—MTSOSD-58, and The Short-Form Health Survey (SF-36), and a question-naire were used to assess the support group process.

Patient identification form
A form consisting of 10 questions was developed by the investigators and used to record demographic and liver disease information. The form included questions about age, gender, marital status, education level, and occupation, and clinical data (eg, cause of liver disease, donor type, living-donor relationship, transplant time, and immunosuppressive therapy).

Knowledge level assessment questionnaire
This is a form developed in the light of the literature to evaluate LTRs’ knowledge of life after liver transplant. It was composed of 15 multiple choice questions. Each question was scored as 1 point. The lowest score obtained was zero and the highest score 15.

The knowledge level assessment questionnaire was developed by the investigators. To test content validity, a total of 7 experts specializing in liver transplant were evaluated. A pilot study was done with 15 LTRs. After studying the questionnaires, the following changes in the questionnaires were made: decreased to knowledge question number in the knowledge level assessment questionnaire. In our study, Cronbach's alpha of Knowledge level assessment questionnaire was found 0.91.

Modified Transplant Symptom Occurrence and Symptom Distress Scale—58—MTSOSD-58
The original English version of this instrument includes 59 items related to symptoms associated with adverse events of traditional and novel immunosuppressive drugs, and assesses the patient’s symptoms associated with the adverse events of immunosuppressive drugs. Each symptom in MTSOSD-58 is scored with respect to symptom occurrence (SO) and symptom distress (SD). Symptom occurrence is assessed on a 5-point rating scale ranging from 0 (never occurring) to 4 (always occurring), and symptom distress is assessed on a 5-point rating scale ranging from 0 (not at all distressing) to 4 (extremely distressing).

The validity of the MTSOSD-59R was well established in Dobbels and associates’ study (2008).22 A Turkish validity and reliability study was performed by Ordin and associates (2013b).²³ The study was applied to liver and kidney transplant recipients (n = 180) and healthy control subjects (n = 180). The Turkish version of the instrument was translated in a culturally sensitive way using forward-backward translation. Content validity was evaluated using the content validity index (content validity index = 1.0). After the content validity was determined, the Turkish version of the instrument was called MTSOSD-58 because 58 items were included. The known-group approach was used to test the construct validity of the instrument. Symptom occurrence and symptom distress are influenced by the sex of the patient, and their depression level. Also, symptom scores of transplant patients taking immunosuppressive drugs were compared with the healthy group that was not taking such medications. Female transplant recipients experienced a higher symptom occurrence (P = .01) and higher symptom distress (P = .01) than did male transplant recipients. Transplant recipients with higher scores for depressive symptoms had a significantly higher mean symptom occurrence and symptom distress scores than did transplant recipients with lower depressive symptom scores (U = 474.000, P = .001; U = 404.500, P < .001). The mean symptom occurrence and symptom distress scores of transplant recipients were significantly higher than those of healthy participants (U= 6495.000, P < .001; U = 8846.500, P < .001). The reliability of the scale was tested using the split half method and was found to be good in the symptom occurrence (.919) and symptom distress (.920) dimensions.²³

The Short-Form Health Survey (SF-36)
The Short-Form Health Survey (SF-36) is the most frequently used instrument to measure health-related quality of life.^5,6 The SF-36 is composed of 35 items and 8 subscales: physical functioning, role physical, bodily pain, vitality, general health, social functioning, role emotion, and mental health. In addition, 1 open-ended question is used to evaluate how health has changed in the preceding year. The possible range of scores for each subscale is 0-100. The 8 subscales can be categorized into 2 constructs: the physical component summary score and mental component summary score.²⁴

The instrument has been evaluated extensively and proved to have good psychometric properties.²⁵ The Cronbach’s alpha for the internal consistency reliability of the Turkish version of SF-36 was 0.75-0.76 for the 8 subscales. The study on the validity of the scale revealed a correlation coefficient of 0.3-0.76 between the subscales of SF-36 and those of the Nottingham Health Profile (NHP).²⁶ The Cronbach’s alpha for the internal consistency reliability was 0.73-0.76 for the SF-36. Because the calculated component of the summary health score for SF-36 varies from country to country, we took account of the data from the study by Demiral and associates (2006),²⁷ who attempted to determine standards of SF-36 in a Turkish population. We assessed social functioning subscale, the physical component summary score and mental component summary score in this study. In our study, the Cronbach’s alpha of SF-36 was between 0.76 and 0.94 for the 8 subscales of SF-36.

A questionnaire for assessment of the support group process
This form was developed to evaluate satisfaction with support group meetings and was composed of 12 questions. Seven questions about feelings about the support group process were scored on a 7-point Likert scale in the form of facial expressions (the lowest degree of satisfaction corresponding to zero and the highest degree of satisfaction corresponding to 5). The lowest score obtained was 0 and the highest was 35. Four open-ended questions were used to reveal the support group process and its effects, and provide the trainer with detailed information.

“A questionnaire for assessment of the support group process questionnaire” was developed by investigators. Content validities of the questionnaires were assessed by experts who specialized in liver transplants. Seven experts evaluated the question-naires. A pilot study was made with 15 LTRs. Cronbach's alpha of “A questionnaire for assessment of the support group process” was found 0.89.

Data analyses
Statistical analyses were performed with SPSS software (SPSS: An IBM Company, version 16.0, IBM Corporation, Armonk, NY, USA). A one-way analysis of variance (ANOVA) and a t test were used to determine between-group differences in the demo-graphic features.

The hypotheses were tested based on the mean scores of MTSOSD-58, the means of the subscales, and the component summary score of SF-36. Hotteling’s T-square analysis was used to determine whether the data were normally distributed.

A primary analysis with repeated-measures ANOVA (RM-ANOVA) with 1 between-group factor was used to compare changes in key variables (symptoms, and QOL) from pretest to posttest 1 and to posttest 2 between the interventional and control conditions. Statistically significant group-by-time interactions were examined for all variables to assess intervention effects.

In the presence of significant differences, the t test for independent groups with the Bonferroni correction or the Mann-Whitney U test was used to determine which group caused the significant differences. One-way variance analysis with the Bonferroni correction or the Friedman test to determine the time during which the difference appeared, and a Bonferroni-corrected paired t test and the Wilcoxon test were used as further analyses when there was a significant difference in the variables from baseline to follow up-1 and to follow up-2. Because a total of 3 comparisons was made on further analyses, P = .016.

It has been suggested that ridit scoring be conducted in studies using any version of MTSOSD. It is an appealing technique for treating ordinal data because it allows researchers to choose a reference distribution, which is indicated by the goal of the research. The use of ridit scoring requires the selection of a reference distribution, and the ridit score of the interest group is compared with the ridit score of a chosen reference group. The ridit score of a reference group must be 0.5.^28,29 In the present study, data collected from the control group were considered the reference group.

Results

Table 1 shows the patient characteristics. The mean age of the participants was 52.38 years (SD = 10.36) in the intervention group and 50.23 years (SD = 11.51) in the control group. The groups had no statistically significant differences in demographic features and liver disease (P > .05). There were no significant dif-ferences between the groups in MTSOSD-58, and component summary scores of SF-36 in the baseline assessment time (Table 2). There were no significant differences between living-and deceased-related liver transplant recipient groups in terms of the component summary scores of SF-36 in the baseline and follow up-2 assessment time in the control and intervention groups (P > .05). The living-related liver transplant recipients group had a significantly higher mean mental component score than the deceased-related liver transplant recipients group in control group (P = .04).

Effects of support group intervention in physical adaptation
In terms of group-by-time interaction, scores for symptoms improved after the intervention (P < .05) (Table 3). The intervention group had significantly lower mean scores for symptom occurrence (follow up-1: U = 460. 000; P < .05) than the control group. Similarly, the ridit score showed a decrease in symptom occurrence and distress at follow up-1, but this positive influence regressed at follow up-2 (ridit score < 0.50) (Figure 2). We found that scores for the physical component summary of SF-36 were significantly lower after the support group intervention by group-by-time interaction (P < .05) (Table 3).

Effects of support group intervention on psychological adaptation
We found that scores of the mental component summary of SF-36 were significantly different after the intervention (P < .05) (Table 3). The intervention group had significantly higher mean scores for the mental component summary (follow up-1: t = 4.397, P < .05, follow up-2 = 3.447, P < .05) subscales than the control group.

Effects of support group intervention on social adaptation
It was found that the scores for the social functioning dimension of SF-36 were significantly different after the intervention (P < . 05) (Table 3). The interventional group had significantly higher mean scores for social functioning (follow up-1: t = 2.754; P < .05). Also, the intervention group had significantly higher mean scores of the support group satisfaction (baseline mean = 31.60, follow-up-1 mean = 31.83, follow-up 2 mean = 31.03, F = .420; P > .05).

We found that the scores of the knowledge level were significantly different after intervention by group-by-time interaction (P < .05) (Table 3). The intervention group had significantly higher scores for knowledge after intervention (follow up-1: t = 5.083, P < .05, follow up-2: t = 6.616; P < .05) than the control group.

Discussion

Effects of support group intervention in physical adaptation
Physiological adaptation refers to patients’ adjustment to their own changing physiological needs. Liver transplant recipients make great efforts to adapt to their lives, and physiological status, which change after transplant. Support groups provide these patients with opportunities to discuss their own activities and exercise, have balanced nutrition, and health checks, which may have had a positive influence on patients’ daily life activities in this study. In addition, our patients shared their experiences and discussed solutions to their problems, which had a positive effect on their physiological adaptation.

In this study, physical adaptation of LTRs was improved positively after the support group intervention. In the literature, similarly to our study, it has been reported that mindfulness meditation group interventions were positively affected sleep^13,14 and the physical health of organ transplant recipients;¹⁴ that physical rehabilitation positively affected physical health;16 that exercise and diet affected physical function and exercise capacity;¹⁷ and that fitness rehabilitation affected physical health and physical behavior.¹⁵

In a study on the effectiveness of an exercise and diet program, patients attending the program had a better exercise capacity in the short term (in the fourth month) than did control patients; however, the positive effect of the program did not continue in the long term (in the tenth month).¹⁷ Support groups should continue to meet, and specific training programs be directed toward exercise, and managing of the adverse events of immunosuppressive therapy should be conducted so that improvement in symptoms can be sustained.

Effects of the support group intervention on psychological adaptation
Two aims of the support group intervention were to provide peer support to reduce stress, and to overcome a disease/incapacity and offer basic knowledge and skills to adapt to changes in social life and health status.⁸ Sharing experiences at each support group meeting, and a specific meeting for psychological support and relaxation exercise, are directed toward enhancing the patients’ adaptation in the self-concept mode.

In this study, the support group intervention was affected by the psychological adaptation of the LTRs. In the literature, mindfulness meditation group intervention was found to decrease anxiety and depression,^3,14 and those members of unstructured support groups improved their coping skills and reduced their anxiety levels.^18,19 In another study, liver transplant candidates who received psycho-social training had improved emotional status and low anxiety levels after the intervention.²¹

Effects of support group intervention on social adaptation
Support groups meet once a month, which offers an opportunity to provide social support for each other, and this in turn improves their social relationships. Nurses also should offer social support to patients after a liver transplant.³⁰ However, in this study, support groups were not found to be effective enough to improve social functions in terms of group-by-time interaction (P > . 05). Further analysis showed a significant improvement in social functions in the intervention group (P < .016).

It has been emphasized that the interaction between liver transplant patients in support groups after transplant has a positive effect on their adaptation to their new lives.³¹ It has also been noted that liver transplant patients need psychological and social support from both their families and health professionals.³² In addition, Keidar and associates (2001a)¹⁸ reported that support group interventions had a positive influence on relationships between the family members of liver, kidney, and pancreas transplant patients. Van Ginneken and associates (2011)¹⁶ showed that exercise and diet improved patients’ autonomy, roles in their families, and social relationships.

The major limitation of this study is that it was not a randomized controlled study. This study’s other limitation is that the results of the study cannot be generalized to other groups of patients because the study included only liver transplant patients and the content of the training was directed toward specific subjects about liver transplant. Our support group was heterogeneous in terms of liver transplant recipients, including both new and long-term patients. The feature was provided to facilitate sharing between new and long-term patients. On the other hand, delete support group intervention can be applied in the early term, which experienced the most problems by patients.

In the current study, we found that the support group intervention significantly increased the liver transplant recipients’ knowledge (P < .05), which continued to increase in the third month after the intervention (P < .016). This increase in knowledge can be explained by patients continuing to benefit from the booklet given to them and the support group interventions were effective in enhancing the patients’ sensitivity toward their condition.

In conclusion, this study revealed that the support group intervention had a positive influence on the physiological, psychological, and social adaptation of liver transplant patients. This effect appeared just after the support group intervention but decreased in the third month after the intervention. The positive effect of the support group intervention on all modes of adaptation can be sustained, support group meetings should be continued, and specific attempts such as the management of the adverse events of drugs, exercise, and psychological support should be planned.

Nurses should form support groups to facilitate liver transplant patients’ adaptation to their new lives after transplant. The focus of support groups should be patients’ problems rather than training given to strengthen patients’ adaptation. Therefore, training and information offered to patients should be completed before liver transplant. Patients who are going to undergo liver transplants should be encouraged to attend training and support group interventions.

References:

1. Ordin YS, Dicle A, Wellard S. Quality of life in recipients before and after liver transplantation in Turkey. Prog Transplant. 2011;21(3):260-267.
   PubMed
2. Bean KB. An exploratory investigation of quality of life in adult liver transplant recipients. Prog Transplant. 2005;15(4):392-396.
   PubMed
3. Nilsson M, Persson LO, Forsberg A. Perceptions of experiences of graft rejection among organ transplant recipients striving to control the uncontrollable. J Clin Nurs. 2008;17(18):2408-2417.
   CrossRef - PubMed
4. Watanabe A, Inoue T. Transformational experiences in adult-to-adult living-donor liver transplant recipients. J Adv Nurs. 2010;66(1):69-81.
   CrossRef - PubMed
5. Bravata DM, Olkin I, Barnato AE, Keeffe EB, Owens DK. Health-related quality of life after liver transplantation: a meta-analysis. Liver Transpl Surg. 1999;5(4):318-331.
   CrossRef - PubMed
6. Tome S, Wells JT, Said A, Lucey MR. Quality of life after liver transplantation. A systematic review. J Hepatol. 2008;48(4):567-577.
   CrossRef - PubMed
7. Jennings AR. Assessing educational needs of potential hepatitis C patients at a Veterans Affairs medical center. Educ Health (Abingdon). 2011;24(3):532.
   PubMed
8. Yalom ID. Grup Psikoterapisinin Teori ve Pratiği. Istanbul: Nobel Medicine Bookshop; 1992.
9. Aktaş AM. Grup Süreci ve Grup Dinamikleri. Ankara: 1st Ed. Ankara: Sistem Yayıncılık; 1997.
10. Ordin YS, Karayurt O, Wellard S. Investigation of adaptation after liver transplantation using Roy's Adaptation Model. Nurs Health Sci. 2013;15(1):31-38.
    CrossRef - PubMed
11. Payne GM, Harrison B. Reducing stress in renal patients and their families: a nurse-managed patient support group. J Nephrol Nurs. 1984;1(3):138-140.
    PubMed
12. Hyler BJ, Corley MC, McMahon D. The role of nursing in a support group for heart transplantation recipients and their families. J Heart Transplant. 1985;4(4):453-456.
    PubMed
13. Gross CR, Kreitzer MJ, Russas V, Treesak C, Frazier PA, Hertz MI. Mindfulness meditation to reduce symptoms after organ transplant: a pilot study. Adv Mind Body Med. 2004;20(2):20-29.
    PubMed
14. Gross CR, Kreitzer MJ, Thomas W, et al. Mindfulness-based stress reduction for solid organ transplant recipients: a randomized controlled trial. Altern Ther Health Med. 2010;16(5):30-38.
    PubMed
15. Gentry AC, Belza B, Simpson T. Fitness support group for organ transplant recipients: self-management, self-efficacy and health status. J Adv Nurs. 2009;65(11):2419-2425.
    CrossRef - PubMed
16. van Ginneken BT, van den Berg-Emons HJ, Metselaar HJ, Tilanus HW, Kazemier G, Stam HJ. Effects of a rehabilitation programme on daily functioning, participation, health-related quality of life, anxiety and depression in liver transplant recipients. Disabil Rehabil. 2010;32(25):2107-2112.
    CrossRef - PubMed
17. Krasnoff JB, Vintro AQ, Ascher NL, et al. A randomized trial of exercise and dietary counseling after liver transplantation. Am J Transplant. 2006;6(8):1896-1905.
    CrossRef - PubMed
18. Kiedar R, Katz P, Nakache R. "Living again": heterogeneous support group for transplant patients and their families. Transplant Proc. 2001;33(6):2930-2931.
    CrossRef - PubMed
19. Keidar R, Katz P, Nakache R. Resuming life after transplantation: development of a support group for patients and their families. Transplant Proc. 2001;33(1-2):1911-1912.
    CrossRef - PubMed
20. Wilkins F, Bozik K, Bennett K. The impact of patient education and psychosocial supports on return to normalcy 36 months post-kidney transplant. Clin Transplant. 2003;17(suppl 9):78-80.
    CrossRef - PubMed
21. Sharif F, Mohebbi S, Tabatabaee HR, Saberi-Firoozi M, Gholamzadeh S. Effects of psycho-educational intervention on health-related quality of life (QOL) of patients with chronic liver disease referring to Shiraz University of Medical Sciences. Health Qual Life Outcomes. 2005;3:81.
    CrossRef - PubMed
22. Dobbels F, Moons P, Abraham I, Larsen CP, Dupont L, De Geest S. Measuring symptom experience of side-effects of immunosuppressive drugs: the Modified Transplant Symptom Occurrence and Distress Scale. Transpl Int. 2008;21(8):764-773.
    CrossRef - PubMed
23. Ordin YS, Karayurt O, Cilengiroğlu OV. Validation and adaptation of the Modified Transplant Symptom Occurrence and Symptom Distress Scale-59 Items Revised into Turkish. Prog Transplant. 2013;23(4):392-400.
    CrossRef - PubMed
24. Turner-Bowker DM, DeRosa MA, Ware JE Jr. SF-36 Health Survey. In: Boslaugh S. Ed. Encyclopedia of Epidemiology. Thousand Oaks, CA: Sage Publications. 2008;2.
    CrossRef
25. Ware JE Jr, Gandek B. Overview of the SF-36 Health Survey and the International Quality of Life Assessment (IQOLA) Project. J Clin Epidemiol. 1998;51(11):903-912.
    CrossRef - PubMed
26. Koçyiğit H, Aydemir Ö, Fişek G, Ölmez N. Memiş A. Reliability and validity of the Turkish version of short form-36 (SF-36): a study in a group of patients with rheumatic diseases [in Turkish]. İlaç ve Tedavi Dergisi. 1999;12:102-106.
27. Demiral Y, Ergor G, Unal B, et al. Normative data and discriminative properties of short form 36 (SF-36) in Turkish urban population. BMC Public Health. 2006;6:247.
    CrossRef - PubMed
28. Sermeus W, Delesie L. Ridit analysis on ordinal data. West J Nurs Res. 1996;18(3):351-359.
    CrossRef - PubMed
29. Bross I D J. How to use ridit analysis. Biometrics. 1958;14:18-38.
    CrossRef - http://dx.doi.org/10.2307/2527727
30. Kendall K, O’Dell MI. Psychosocial issues in transplantation. In: Ohler L, Cupples S, eds. Core Curriculum for Transplant Nurses. International Transplant Nurses Society. Mosby Elsevier, 2007.
31. Sargent S, Wainwright SP. A qualitative study exploring patients perceived quality of life following an emergency liver transplant for acute liver failure. Intensive Critical Care Nursing. 2007;23(5):272-280.
    CrossRef - PubMed
32. Jones JB. Liver transplant recipients' first year of posttransplant recovery: a longitudinal study. Prog Transplant. 2005;15(4):345-352.
    PubMed