instruction: what are the number of patients who have had a cholesterol ratio (total/hdl) test until 2101?
response: SELECT COUNT(DISTINCT admissions.subject_id) FROM admissions WHERE admissions.hadm_id IN (SELECT labevents.hadm_id FROM labevents WHERE labevents.itemid IN (SELECT d_labitems.itemid FROM d_labitems WHERE d_labitems.label = 'cholesterol ratio (total/hdl)') AND STRFTIME('%y', labevents.charttime) <= '2101')