Impact of prior admissions on 30-day readmissions in Medicare heart failure inpatients

Objective: To determine how all-cause hospitalizations within 12 months preceding an index heart failure (HF) hospitalization affect risk stratification for 30-day all-cause readmission. Patients and Methods: Early readmission of inpatients with HF is challenging to predict, yet this outcome is used to compare hospital performance and guide reimbursement. Most risk models do not consider the potentially important variable of prior admissions. We analyzed Medicare inpatients with HF aged 66 years or older admitted to 14 Michigan community hospitals from October 1, 2002, to March 31, 2003, and from January 1 to June 30, 2004. Clinical data were obtained from admission charts, hospitalization dates from Centers for Medicare & Medicaid Services (CMS) claims, and mortality dates from the Social Security Death Index. We used mixed-effects logistic regression and reclassification indices to evaluate the ability of a CMS chart-based readmission risk model, prior admissions, and their combination to predict 30-day readmission in survivors of the index HF hospitalization. Results: Of 1807 patients, 43 (2.4%) died during the index admission; 476 of 1764 survivors (27%) were readmitted 30 or fewer days after discharge. Adjusted for the CMS readmission model, prior admissions significantly increased the odds of 30-day readmission (1 vs 0: odds ratio, 4.67; 95% CI, 3.37-6.46;2 vs 0: odds ratio, 6.49; 95% CI, 4.93-8.55; both P<.001), improved model discrimination (c statistic, 0.61-0.74, P<.001), and reclassified many patients (net reclassification index, 0.40; integrated discrimination index, 0.12). Conclusion: In Medicare inpatients with HF, prior all-cause admissions strongly increase all-cause readmission risk and markedly improve risk stratification for 30-day readmission.