when did patient 67468 get in their last hospital encounter a lab test for the last time?
select labevents.charttime from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 67468 and admissions.dischtime is not null order by admissions.admittime desc limit 1 ) order by labevents.charttime desc limit 1