during the first hospital visit, when did patient 52598 first receive a lab test?
select labevents.charttime from labevents where labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 52598 and admissions.dischtime is not null order by admissions.admittime asc limit 1 ) order by labevents.charttime asc limit 1