The thromboembolic event rate was low in the modified preparation group ( 1 of 63 [ 1.6 % ] ) compared with the standard preparation group ( 7 of 63 [ 11.1 % ] ; adjusted risk difference , -11.7 % [ 95 % CI , -21.3 % to -2.0 % ] ; P = .02 ) , which had a higher thromboembolic risk than the non-HTPR group ( 1 of 102 [ 1.0 % ] ; adjusted risk difference , 8.6 % [ 95 % CI , 1.0 % to 16.3 % ] ; P = .03 ) .