compare the new sample in a high sampling rate datalogger

Hi guys, I am using sdFat library the analog bin logger example,

the thing is, this high speed datalogger uses interrupts and timers to make the ADC work at a pre-determined sampling frequency and it DOES NOT use the normal analogRead () function

my question is, how can I compare the new sample in the analog bin logger example as I simply want to compare the new sample as in

if ( analogRead() < 256 ) {// do something}

knowing that there is no analogRead() in the program because it uses timers and interrupts