Validation of a 28 day interval between discharge and readmission for emergency readmission rates.

For the majority of studies on hospital readmission rates, a readmission is deemed to have occurred if a patient was admitted within 28 days of the previous discharge date. This time period, however, has rarely been justified clinically or statistically and certainly not in Australia. In examining the patterns of readmissions to NSW public acute hospitals, this study provides statistical support for the use of a 28 day interval for total readmissions. The same finding applies to the four admission categories of medical, surgical, paediatrics, and obstetrics and gynaecology.