instruction: count the number of times patient 15754 was tested for mch in 2104.
response: SELECT COUNT(*) FROM labevents WHERE labevents.itemid IN (SELECT d_labitems.itemid FROM d_labitems WHERE d_labitems.label = 'mch') AND labevents.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 15754) AND STRFTIME('%y', labevents.charttime) = '2104'