count the number of patients who had received a microbiological test of the biopsy until 2104.
select count( distinct admissions.subject_id ) from admissions where admissions.hadm_id in ( select microbiologyevents.hadm_id from microbiologyevents where microbiologyevents.spec_type_desc = 'biopsy' and strftime('%y',microbiologyevents.charttime) <= '2104' )