###HUMAN: what is the total number of patients diagnosed with icd9 code 45620 who had a blood test., ###ASSISTANT: 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 = "45620" AND lab.fluid = "Blood"