instruction: what is the first value of the sodium lab test of patient 006-14121 since 12/2105?
response: SELECT 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 = '006-14121')) AND lab.labname = 'sodium' AND STRFTIME('%y-%m', lab.labresulttime) >= '2105-12' ORDER BY lab.labresulttime LIMIT 1