how many patients were diagnosed with autoimmun hemolytic anem in hospital and didn't come back to the hospital in the same month in this year?
select ( select count( distinct t1.subject_id ) from ( select admissions.subject_id, diagnoses_icd.charttime from diagnoses_icd join admissions on diagnoses_icd.hadm_id = admissions.hadm_id where diagnoses_icd.icd9_code = ( select d_icd_diagnoses.icd9_code from d_icd_diagnoses where d_icd_diagnoses.short_title = 'autoimmun hemolytic anem' ) and datetime(diagnoses_icd.charttime,'start of year') = datetime(current_time,'start of year','-0 year') ) as t1 ) - ( select count( distinct t2.subject_id ) from ( select admissions.subject_id, diagnoses_icd.charttime from diagnoses_icd join admissions on diagnoses_icd.hadm_id = admissions.hadm_id where diagnoses_icd.icd9_code = ( select d_icd_diagnoses.icd9_code from d_icd_diagnoses where d_icd_diagnoses.short_title = 'autoimmun hemolytic anem' ) and datetime(diagnoses_icd.charttime,'start of year') = datetime(current_time,'start of year','-0 year') ) as t2 join admissions on t2.subject_id = admissions.subject_id where t2.charttime < admissions.admittime and datetime(admissions.admittime,'start of year') = datetime(current_time,'start of year','-0 year') and datetime(t2.charttime,'start of month') = datetime(admissions.admittime,'start of month') )