calculate the number of times until 3 years ago patient 19691 has received a mcv lab test.
select count(*) from labevents where labevents.itemid in ( select d_labitems.itemid from d_labitems where d_labitems.label = 'mcv' ) and labevents.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 19691 ) and datetime(labevents.charttime) <= datetime(current_time,'-3 year')