How to Calculate 30-Day Readmission Rate

This  rate  is  calculated  by  identifying individual  residents admitted to the facility after an inpatient hospital stay during a given a given period of time, usually calculated on a monthly basis, and following them for 30 days.
a. The denominator for  this  calculation is the  number  of residents admitted to  your facility who have had an inpatient hospital stay during the month.
The numerator is the number of inpatient hospitalizations among   these   residents that   occur within   30-days   of admission to your facility after an inpatient hospital stay.
b. Residents sometimes have two (or even more) 30-day readmissions in a 30 day period.
Each  admission  to  your  facility  after  an  inpatient  stay  should  be  counted  in  the denominator, and inpatient hospitalizations within 30-days of the most recent admission to your facility after an inpatient hospital stay should be counted in the numerator. Thus, one resident could contribute two or more times to the 30-day readmission rate.

c. The  earliest  you  can  calculate  the  readmission  rate  for  a  given  month  is  31 days  after the end of the month, because a resident admitted on the last day of the month is at risk of a 30-day readmission for the 30 day period following admission.
d. There are some commonly asked questions about this calculation:
1) What  if  the  resident  is  discharged  before  their  30-day  risk  period  is  over?
As  a practical  matter,  it  is  difficult  for  a  facility  to  follow  up  to  determine  if  a  30-day readmission occurred, so your rate will be contingent upon the resident being in the facility.  However,  the  current  version  of  the  CMS  definition for  30-day  readmissions from SNFs does include the entire 30-day period of risk of readmission.
2)What  if  the  resident  went  home  or  was  admitted  to  another  SNF,  LTAC,  or  other post-acute facility before being admitted to your facility?
This occurs in less than 10% of  Medicare  fee-for-service  patients  admitted  to  SNFs  from  hospitals.  The  current version  of  the  CMS  definition  for  30-day readmissions  from  SNFs  does  include  the entire  30-day  period  of  risk  of  readmission,  including  any  time  not  spent  in  your facility after hospital discharge.
3) What if the resident is readmitted, but to observation status?
They do not count in the numerator. Observation status is considered outpatient care by CMS, so these stays  do not count as readmission.
Example: Your census in January was 110, in February 112, and in March 108. During these  3  months  you  had  66  admissions  from your  local  hospital,  and  through  April  30, you  transferred a  total  of 40  residents  to  the  hospital.  Of  these  40,  one  was  directly readmitted for a planned revision of a colostomy, a second for a scheduled replacement of  a  displaced  artificial  hip,  and  one  for  monthly  chemotherapy.  Five  residents  were admitted  into  observation  status.
What  was  your 30-day  readmission  rate for  this quarter?
The answer is 33%. The denominator is 66. The numerator is 32 (40 minus the 3 residents with planned readmissions, and the five admitted into observation status).