Análisis del sistema de alistamiento y priorización para trasplante hepático de adultos en Chile

Background: In Chile, organ allocation for liver transplantation (LT) in adults is prioritized according to the MELD-Na score. Exceptions such as Hepatocellular Carcinoma (HCC) and other non-HCC exceptions receive a score called Operational MELD score. Aim: To evaluate the effectiveness of the MELD-Na score and the operational MELD score as a prioritization system for LT in Chile. Material and Methods: Retrospective analysis of the waiting list (WL) of adult candidates (≥ 15 years) for elective LT in Chile from 2011 to 2017. The probability of leaving the WL, defined by death or contraindication for LT was compared in three groups: 1) Cirrhotic patients prioritized according to their real MELD-Na score (CPM), 2) HCC and 3) other non-HCC exceptions. Results: We analyzed 730 candidates for LT, with a median age of 57 years, 431 (56%) were men. In the study period, 352 LT were performed (48%). The annual exit rate was significantly higher in the CPM group (45.5%) compared to HCC (33.1%) and non-HCC (29.3%), (p < 0.001). Post LT survival was 86% at 1 year and 85% at 5 years, without significant differences between groups. In the CPM group, post-transplant survival was significantly lower (p < 0.05) in patients with MELD-Na ≥ 30 at transplant (81% per year) compared to patients with patients with MELD-Na < 30 (91% per year). Conclusions: MELD-Na score can discriminate very well patients who have a higher risk of death in the short and medium term. However, the assignment of operational scores for situations of exception produces inequities in the allocation of organs for LT and must therefore be carefully adjusted.

Situación actual del trasplante hepático pediátrico por hepatopatías crónicas en Chile: Inequidades asociadas a la priorización por sistema MELD/PELD

Background: The Chilean allocation system for liver transplantation (LT) uses the MELD/PELD score to prioritize candidates on the waiting list. Aim: To assess if the Chilean allocation system for LT is equitable for pediatric candidates compared to their adult counterparts. Material and Methods: We used the Public Health Institute's registry between October 2011 and December 2017. We analyzed candidates with chronic hepatic diseases listed for LT. The primary outcome was the cadaveric liver transplantation (CLT) rate. Secondary outcomes were death or disease progression in the waiting list and living donor liver transplant (LDLT) rate. Results: We analyzed 122 pediatric and 735 adult candidates. Forty one percent of pediatric candidates obtained a CLT compared to 48% of adults (p = NS). Among patients aged under two years of age, the access to CLT on the waiting list there was 28% of CLT, compared to 48% in adults (p = 0.001). Fifty-seven percent of candidates aged under two years were listed for cholestatic diseases, obtaining a CLT in 18% and requiring a LDLT in 49%. The median time in the waiting list for CLT was 5.9 months in pediatric candidates and 5.1 in adults, while the median time to death in the waiting list was 2.8 and 5.6 months, respectively. The mortality rate at one year in candidates under two years old was 38.1% compared to 32.5% in adults. Conclusions: Pediatric candidates with chronic liver diseases, especially under two years of age, have greater access difficulties to CLT than adults. Half of the pediatric candidates die on the waiting list before three months. The mortality among candidates under two years of age in the waiting list is excessively high.

Inmunología del transplante / Immunology in transplants

Los principales sistemas genéticos en alotrasplantes del hombre son el grupo sanguíneo ABO, complejos menores de histocompatibilidad y complejo mayor de histocompatibilidad (CMH). Este último tiene expresión vaariable en los diferentes tejidos, siendo interferón * el principal inductor de la expresión de estas moléculas. El CMH por su rol biológico desempeña un papel central en la inducción y como blanco de la respuesta inmune contra el injerto. Linfocitos T helper, linfocitos T citotóxicos, macrófagos y anticuerpos participan en la producción del daño tisular. Diferentes métodos se han utilizados para evitar el rechazo, dependiendo de las características del tejido u órgano a trasplantar