NEW YORK (Reuters Health) Dec 27 - The current U.S. system for allocating donated livers - which is based on the Model for End-Stage Liver Disease (MELD) score - is fair to patients with chronic liver disease whether they're waiting for a first transplant or a retransplant, a new study shows.
The MELD score, adopted in 2002, considers the patient's bilirubin level, creatinine level, and international normalized ratio. Increasing scores indicate a higher short-term risk for death without a transplant.
Patients with fulminant liver failure, or those who've just had a transplant but have primary graft nonfunction or early hepatic artery thrombosis, always move to the top of the waiting list, with a "status 1" priority.
But patients with chronic liver disease compete under the same system whether they're waiting for a retransplant or a primary transplant. Patients and doctors have wondered whether chances of a new liver - and odds of survival -- differ depending on whether a candidate has already been transplanted before.
In a study reported online November 10th in the American Journal of Transplantation, Dr. H. J. Kim and colleagues from the Mayo Clinic in Rochester, Minnesota compared the two groups' mortality rates within six months of being listed for transplant with a given MELD score. They also compared current findings to results in a pre-MELD era.
"The main finding in our analysis is that in the MELD score ranges where most liver transplantation is performed, there were no large differences in waitlist mortality given a MELD score," the researchers report. "In our opinion, the difference was not large enough to warrant an adjustment in the allocation system."
They had data on roughly 30,000 patients who joined the waiting list in the MELD era (including nearly 1400 needing retransplant), and roughly 15,000 registered in the two years before MELD was adopted (with almost 700 needing retransplant).
In the MELD era, retransplant candidates had higher median scores at the time of registration than primary transplant candidates (21 versus 15, respectively), and this likely contributed to the higher 6-month waiting list mortality among retransplant candidates on an unadjusted Kaplan-Meier analysis.
As expected, MELD score at registration was associated with increasing risk of death on multivariate analysis -- but the slope of the survival curve was slightly steeper for primary transplant candidates than for retransplant candidates. As a result, the risk of death in retransplant candidates was higher than that for primary transplant candidates in the low MELD score range and lower than that for primary transplant candidates in the high MELD score range.
The probability of actually receiving a liver transplant within 6 months of registration increased substantially from the pre-MELD era (28% for retransplant candidates, 19% for primary transplant candidates) to the post-MELD era (54% for retransplant candidates, 35% for primary transplant candidates).
Six-month waitlist mortality also decreased significantly between the periods (from 18% to 14% for retransplant candidates and from 9.3% to 8.0% for primary transplant candidates).
"This analysis contributes to the dialogue by providing a quantitative basis upon which philosophical and ethical considerations may be made," the investigators conclude. "In the meantime, we are mostly comforted by the fact that MELD, shown here again as a strong indicator of waitlist mortality, has contributed to a significant increase in the probability of receiving transplantation under the current allocation system."
Am J Transpl 2010.