how many days has it been from the last time patient 31854 received a glucose lab test on this hospital encounter?
select 1 * ( strftime('%j',current_time) - strftime('%j',labevents.charttime) ) from labevents where labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'glucose' ) and labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 31854 and admissions.dischtime is null ) order by labevents.charttime desc limit 1