what are the numbers of patients who were tested for absolute cd8 count until 1 year ago?
select count( distinct admissions.subject_id ) from admissions where admissions.hadm_id in ( select labevents.hadm_id from labevents where labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'absolute cd8 count' ) and datetime(labevents.charttime) <= datetime(current_time,'-1 year') )