instruction: what test was given to patient 10855 the first time this month?
response: SELECT d_labitems.label FROM d_labitems WHERE d_labitems.itemid IN (SELECT labevents.itemid FROM labevents WHERE labevents.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 10855) AND DATETIME(labevents.charttime, 'start of month') = DATETIME(CURRENT_TIME(), 'start of month', '-0 month') ORDER BY labevents.charttime LIMIT 1)