instruction: how many patients have undergone a sputum, tracheal specimen test since 5 years ago?
response: SELECT COUNT(DISTINCT patient.uniquepid) FROM patient WHERE patient.patientunitstayid IN (SELECT microlab.patientunitstayid FROM microlab WHERE microlab.culturesite = 'sputum, tracheal specimen' AND DATETIME(microlab.culturetakentime) >= DATETIME(CURRENT_TIME(), '-5 year'))