what's the name of the test that patient 87733 first had until 05/2104.
select d_labitems.label from d_labitems where d_labitems.itemid in ( select labevents.itemid from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 87733 ) and strftime('%y-%m',labevents.charttime) <= '2104-05' order by labevents.charttime asc limit 1 )