Hospital readmission rates are adjusted for risk for a number of variables to allow for more accurate comparisons across health systems. Risk adjustment is a mathematical method that attempts to account for differences in the patient population and the type of procedures performed in a particular hospital so that hospitals can be compared fairly. Risk adjustment is made to account for differences in the case mix (depending on the disease of the hospital patients) and differences in the performance mix (depending on the complexity of the services provided by the hospital). No risk adjustments are made to account for socio-economic or demographic differences in the patient population to avoid forcing hospitals serving low-income patients to lower standards of care. [11] We used survey design variables to report nationally weighted estimates of proportions and confidence intervals (CIs) to 95% of IS patients with 30-day readmission. Shares are also reported for forecasts in relation to unforeseen, potentially avoidable and causes of recovery. We performed logistic regression analyses to investigate factors associated with 30-day recovery. Adjusted odds ratios and a 95% CI for a 30-day readmission are reported in patients undergoing recanalization therapy (tPA or intravenous IAT). Detailed statistical methods are available in the online data supplement only. There is still a need to identify potentially preventable readmissions and strengthen the transition of care systems so that medical care goes beyond acute hospitalizations to effectively curb recovery.

We analysed demographic data associations such as age, gender, insurance status and household income with 30 days of readmission. In addition, the Charlson comorbidity index (CC) and other individual comorbidities were analyzed. We also looked at differences in length of stay and hospital costs between readmitted and unapproved patients. We performed subgroup analyses in patients aged >65 years and in patients discharged from home after indexed admission. For more information about methods, see the definition section at the end of this brief description. The readmission rate is defined as the frequency with which patients were admitted alive several times within 30 days of their discharge from a first hospital stay, divided by the total number of first stays between January and November 2008. Each hospital stay can be a new first stay. Thus, a patient can have several first stays, regardless of the time that has elapsed between admissions. For example, if an authorization is on January 10 and the next authorization is January 20, followed by a third authorization on January 27 and a fourth on March 30, all four are counted in the denominator of readmission rates. Approvals of January 20 and January 27 are counted at the counter for 30-day retakes of admission on January 10. Admission on January 27 also counts as a 30-day resumption of the January 20 check-in.

The stay of March 30 is not considered a resumption, because it is outside the 30-day window of a previous stay. The final count is 4 initial hospitalizations with three 30-day readmissions. Excluded from the analysis are dismissals with missing age, expected payer, length of stay or main diagnosis as well as dismissals without valid DRG. Discharges for patients who died during a first stay or whose first stay took place in December 2008 were also disqualified because they could not be followed for 30 days. If a patient was transferred to another hospital on the same day or the next day after being discharged from the previous stay, the two admissions were combined into a single stay. The transfers were therefore not considered readmission. Essentially, the projected readmission rate for a hospital with a small number of cases is shifted to the overall U.S. national readmission rate for all hospitals. Recovery estimates for hospitals with few patients will rely heavily on aggregated data for all hospitals, making it less likely that smaller hospitals will fall into one of the outlier categories. This pooling provides a “borrowing of statistical strength” that creates greater confidence in the results.

To classify hospital performance, extremely small hospitals are reported separately. The standard reference point used by the Centers for Medicare & Medicaid Services (CMS) is the 30-day readmission rate. Rates in the 80th percentile or less are considered optimal by CMS. In 2008, one in five non-surgical hospitalizations resulted in a 30-day recovery for all payers and age groups. For non-surgical hospitalizations for acute illnesses, the 30-day readmission rate was 18.0% among payers and age groups. For similar hospitalizations for chronic diseases, the 30-day readmission rate was higher at 22.7%. For insured adults under the age of 65, 30-day readmission rates for non-surgical hospitalizations for acute illnesses ranged from 10.6% to 23.4% depending on payers and age groups. In comparison, readmission rates for chronic diseases were consistently higher, ranging from 15.7 to 28.4 percent. .