Background. Waiting time to liver transplantation (LTx) has dramatical
ly lengthened, but the proportion of candidates who die awaiting trans
plantation has not increased, We evaluated whether longer waiting time
for LTx candidates increases mortality, Methods. A cohort of candidat
es listed for LTx between 1990 and 1993 by three large transplantation
programs was followed for 2 years, The exposure measure was ABO blood
type, which is not inherently related to outcome, but is a major dete
rminant of waiting time, The main outcome measure was a-year mortality
, as evaluated by logistic regression analysis that controlled for dif
ferences in clinical status at the time of evaluation for LTx. Results
., The 308 candidates with type O blood waited longer for LTx (median
109 days) than the 399 candidates with other blood types (median 58 da
ys) (P=0.001), Candidates listed for LTx with type O blood had better
clinical status at evaluation, but then had higher pretransplantation
mortality (13.3%) than other candidates (7.0%) (P=0.005). Blood group
O candidates had higher a-year mortality (26.6%) than other candidates
(22.1%), which on multivariate analysis resulted in a mortality odds
ratio at 2 years of 1.52 (95% confidence interval=1.04-2.23). With the
difference in median waiting time between blood groups increasing fro
m 44 days in the first year to 108 days in the third year, the a-year
mortality odds ratio also rose from 0.94 to 1.97., Conclusions, When c
ompared with LTx candidates with other blood types, blood type O candi
dates have longer waiting times and higher pretransplantation mortalit
y, which results in higher a-year mortality.