how many patients until 2104 were given a wbc casts test?
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 = 'wbc casts' ) and strftime('%y',labevents.charttime) <= '2104' )