The interaction of treatment with race or ethnic
group was not significant, but race or ethnic group
alone had a significant effect on the outcome
(P=0.006). Overall failure rates among non-Hispanic
blacks, Hispanics, and non-Hispanic whites
were 52.8%, 45.0%, and 36.6%, respectively. The
failure rate among American Indians was 39.0%,
although these participants were not included in
the analysis by race or ethnic group owing to small
numbers. Metformin alone was less effective in
non-Hispanic blacks, with 66.2% reaching the
primary outcome, than in either non-Hispanic
whites (44.9%, P=0.01) or Hispanics (44.0%,
P