The purpose of this study was to provide data for developing criteria to accurately assess the risk of post-transplant outcome. To achieve this, we determined the distribution of SIPAT scores among organ transplant recipient candidates, examined the differences in scores by organ, and compared the SIPAT scores for each organ according to demographic data. We found that the liver recipient candidates had higher scores than heart recipient candidates. Regarding subscale scores, the liver and kidney recipient candidates had higher scores than heart recipient candidates on SIPAT B (social support system). The liver recipient candidates had higher scores than kidney recipient candidates on SIPAT C (psychological stability and psychopathology). Additionally, recipient candidates with a history of psychiatric treatment and those who were not employed had very poor overall SIPAT scores. However, there were no differences in SIPAT scores by age, sex, or educational background.
Comparison of SIPAT Total Scores by Organ
Previous studies on SIPAT presented data from several countries including the United States, Spain, Italy, and Thailand. However, many previous studies described only the total SIPAT scores or score distributions [16, 17, 21, 26] and few studies provided comparisons of SIPAT scores among different organs. The total SIPAT score in the present study was 20.03. The total SIPAT score in a previous Thai study of heart, liver, and kidney transplant recipient candidates was 19.65 [27], and the total score in a previous Spanish study of heart, liver, and allogeneic hematopoietic stem cell transplant recipient candidates was 26.0 [21]. The total SIPAT score in a previous American study of heart, lung, liver, and kidney recipient candidates was 12.9 [16]. Thus, differences in total SIPAT scores have been observed in previous studies. It is unclear whether the differences were because of the characteristics of the organs, transplantation conditions in the countries, evaluator, or translation from English to other languages. For these reasons, we believe that for the SIPAT to be used in clinical practice, it is necessary to indicate the evaluation criteria for each country. In our study, the liver recipient candidates had significantly higher SIPAT scores than the heart recipient candidates. In a Thai SIPAT study on the same organs as those in the present study [27], the heart and liver recipient candidates had higher scores than kidney recipient candidates. The reasons for the differences in SIPAT scores by organ may reflect the variations in transplant-related information and patient education provided by transplant teams for each organ to recipient candidates as well as the differences in psychosocial status due to differences in the severity of each disease and course of organ failure. Therefore, the information and patient education provided by transplant teams to recipient candidates should include organ-specific information. Furthermore, it is necessary to equalize the support provided by transplant teams to the recipient candidates for different organs. In Japan, it would be meaningful to provide assessment-based support to liver recipient candidates with high SIPAT scores.
A comparison of SIPAT scores based on demographic data showed that scores of recipient candidates with a history of psychiatric treatment for all organs were higher than the scores of recipient candidates with no history of psychiatric treatment. In a study of kidney transplant recipients in the United States, men had higher scores than women, those with renal impairment secondary to hypertension had higher scores than those with renal impairment because of other causes, and those with low education levels had higher scores than those with high school education [15]. In this study, however, there were no differences in scores based on sex and educational background. This suggests that the use of J-SIPAT in clinical practice in Japan does not need to be revised in terms of these aspects.
Comparison of SIPAT Subscale Scores by Organ
The SIPAT subscales are classified into four domains [14]. As with the total scores, differences in subscale scores between the organs are expected but have rarely been noted in previous studies. The analysis of the subscales revealed that the liver and kidney recipient candidates scored significantly higher than heart recipient candidates on SIPAT B, and the liver recipient candidates scored significantly higher than the kidney recipient candidates on SIPAT C. These organ-specific differences may be explained by the question items. The liver recipient candidates scored higher on items of residential settings (8), organic psychiatric disorders (10), cognitive assessment (11), and overall risk of psychiatric problems (13). In a previous study in Thailand, the scores on SIPAT A were higher for heart and liver recipient candidates than for kidney recipients, the scores on SIPAT B were higher for heart recipient candidates than for liver and kidney recipient candidates, and the scores on SIPAT D were higher for liver recipient candidates [27]. The difference between Japanese and Thai results in the scores of heart recipient candidates may reflect the differences in transplant-related education provided to recipient candidates in the two countries and differences in the severity of the condition of the eligible patients. Another peculiarity of the Japanese transplant situation is the long waiting period for brain-dead donors [28]. The SIPAT scores of the heart recipient candidates in this study were low for the items of medical visits and adherence (4) and availability of social support systems (6).
Good adherence to medical visits and social support during the long transplant waiting period are important for candidates who are on the transplantation waitlists. The transplant candidates in this study were patients who were judged by the transplant team to be likely candidates for organ transplantation. Therefore, it is possible that patients were not placed on the transplant waiting list because the transplant team determined that the patient was not suitable for organ transplantation because of lack of social support or non-adherence issues. It is possible that patients with high psychosocial risk (i.e., high scores on the SIPAT) were not included in this study.
Limitations and Future Steps/Research
This study had several limitations. First, this was a single-center study. Although the facility performs a large number of organ transplantations, there are many other transplantation facilities in Japan. There may be differences in patient education among the facilities, and these differences may affect the SIPAT scores. Furthermore, our analysis did not consider differences by facility, including regional differences. Second our analysis only included heart, liver, and kidney transplant recipient candidates; therefore, the results may not be applicable to other organs. Considering the application of SIPAT in recipient candidates for a wide range of organs, it is necessary to clarify the characteristics of SIPAT for organs that were not included in this study. In addition, many heart recipient candidates in Japan are required to wait for long periods, during which time they may undergo implantation of ventricular assist devices [31, 32]. Therefore, we believe it is necessary to clarify the SIPAT scores specific to patients with ventricular assist devices on the transplant waiting list.
Our study clarified the association between SIPAT and post-transplant outcomes by each organ. Once it is clear that J-SIPAT predicts post-transplant outcomes, the early evaluation of recipient candidates followed by timely interventions can improve post-transplant outcomes. Larger datasets are needed to clarify the association between SIPAT and post-transplant outcomes. Finally, although previous studies have used a four-point scale based on the total SIPAT score, it is not clear whether this evaluation method is available in Japan. Comparisons with other countries showed different mean scores and distributions; therefore, the cut-off scores of J-SIPAT need to be confirmed for the Japanese population.