what's the five most frequently taken lab test until 2100?
select d_labitems.label from d_labitems where d_labitems.itemid in ( select t1.itemid from ( select labevents.itemid, dense_rank() over ( order by count(*) desc ) as c1 from labevents where strftime('%y',labevents.charttime) <= '2100' group by labevents.itemid ) as t1 where t1.c1 <= 5 )