instruction: What is the total number of patients who were diagnosed with icd9 code 4260 and had a cerebrospinal fluid (csf) lab test?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE diagnoses.icd9_code = "4260" AND lab.fluid = "Cerebrospinal Fluid (CSF)"