instruction: when did patient 30044 for the last time until 07/2100 receive the ptt test?
response: SELECT labevents.charttime FROM labevents WHERE labevents.itemid IN (SELECT d_labitems.itemid FROM d_labitems WHERE d_labitems.label = 'ptt') AND labevents.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 30044) AND STRFTIME('%y-%m', labevents.charttime) <= '2100-07' ORDER BY labevents.charttime DESC LIMIT 1