instruction: how many days has it been since the last time during this hospital encounter that patient 19412 had received a red blood cells laboratory test?
response: SELECT 1 * (STRFTIME('%j', CURRENT_TIME()) - STRFTIME('%j', labevents.charttime)) FROM labevents WHERE labevents.itemid IN (SELECT d_labitems.itemid FROM d_labitems WHERE d_labitems.label = 'red blood cells') AND labevents.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 19412 AND admissions.dischtime IS NULL) ORDER BY labevents.charttime DESC LIMIT 1