Expanding Post-Discharge Readmission Metrics in Patients with Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a common and costly reason for hospitalization and rehospitalization. The Hospital Readmissions Reduction Program penalizes hospitals for excess, non-elective, all-cause 30-day, inpatient rehospitalizations for COPD. We sought to determine how broadening the outcome definition would alter the numbers of patients being counted, specifically if observation stays and patients who died in the post-discharge period were included.

We performed a retrospective cohort study of patients hospitalized for COPD between July 1, 2010 and December 31, 2017 in 21 hospitals in the Kaiser Permanente Northern California health care system. We classified encounters into 3 outcomes groups based on a 30-day post-discharge observation period: Group (1) non-elective, all-cause, inpatient rehospitalizations, which is the current metric; Group (2) composite outcome of Group 1 or all-cause mortality; and Group (3) composite outcome of Group 1 or non-elective, all-cause, observation rehospitalization. We used the Box-Cox method to find the transformation of the cumulative curves that resulted in the smallest mean standard error. We used the slope of the transformed curve against days to test for significant differences between pairs of cumulative density curves.

Of 1,384,025 hospitalizations, 11,304 encounters from 8097 patients met criteria to be index hospitalizations. The event rate for non-elective, all-cause, inpatient rehospitalizations was 17.1% (95% CI 10.4-26.5). The event rate for all-cause mortality was 4.7% (95% CI 3.1-7.7). The event rate for non-elective observation rehospitalizations was 3.9% (95% CI 1.7-7.0). The slope and standard error for Group 1 were 1.17 and 0.01, respectively, while the slope and standard error for Group 2 were 1.62 and 0.01, respectively (P=0.02 comparing Groups 1 and 2). The slope and standard error for Group 3 were 1.45 and 0.01, respectively (P=0.02 comparing Groups 1 and 3).

We show that adding outcomes such as mortality and observation rehospitalizations would change the counts of patients contributing to the Hospital Readmission Reduction Program penalty for COPD if the outcome were broadened. Including mortality or observation stays in the quality incentive program might incentivize hospitals and providers to prevent these events in addition to inpatient rehospitalizations.