instruction: give me the number of patients with hematology lab test category who were diagnosed with disruption of external operation (surgical) wound.
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.short_title = "Disrup-external op wound" AND lab."CATEGORY" = "Hematology"