instruction: provide the number of patients whose admission year is less than 2184 and diagnoses long title is thrombocytopenia, unspecified?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id WHERE demographic.admityear < "2184" AND diagnoses.long_title = "Thrombocytopenia, unspecified"