instruction: until 1 month ago, what was the monthly maximum value of the vancomycin - random of patient 015-67291?
response: SELECT MAX(lab.labresult) FROM lab WHERE lab.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.patienthealthsystemstayid IN (SELECT patient.patienthealthsystemstayid FROM patient WHERE patient.uniquepid = '015-67291')) AND lab.labname = 'vancomycin - random' AND DATETIME(lab.labresulttime) <= DATETIME(CURRENT_TIME(), '-1 month') GROUP BY STRFTIME('%y-%m', lab.labresulttime)