was there a urea nitrogen lab test performed on patient 15945 in 12/2105?
select count(*)>0 from labevents where labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'urea nitrogen' ) and labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 15945 ) and strftime('%y-%m',labevents.charttime) = '2105-12'