when was the first time patient 11080 had a anion gap laboratory test?
select labevents.charttime from labevents where labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'anion gap' ) and labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 11080 ) order by labevents.charttime asc limit 1