instruction: count the number of patients who had received a microbiological test of the stem cell - blood culture until 2103.
response: SELECT COUNT(DISTINCT admissions.subject_id) FROM admissions WHERE admissions.hadm_id IN (SELECT microbiologyevents.hadm_id FROM microbiologyevents WHERE microbiologyevents.spec_type_desc = 'stem cell - blood culture' AND STRFTIME('%y', microbiologyevents.charttime) <= '2103')