Postoperative readmission rates correlated with length of stay and ASA class

Image: PD 

1. ASA class and LOS are significant predictors of 30-day readmission after surgical procedures. 

2. A prediction model created by authors based on the factors above can be used to identify patients with higher risk of readmission. 

Evidence Rating Level: 2 (Good)            

Study Rundown: This study evaluated factors associated with increased postoperative 30-day readmission rates, which are now used for adjusting rates of Medicare reimbursement. Multiple variables, including type of surgery, patient comorbidities and post-procedure complications were associated with higher risk of readmission. Multivariate analysis demonstrated that ASA class and length of hospital stay were most significantly associated and were used to create a readmission score as a predictive model for readmission risk. This study included data from a large number of patients across over three hundred hospitals collected by the American College of Surgeons. However, the ACS-NSQIP records 30-day post-surgery readmission rates rather than post-discharge rates, creating an “immortal person-time bias” or time during which a patient cannot be readmitted as they are still at the hospital. This study was limited by the fact that only patients with LOS shorter than 10 days were included in the analysis, likely skewing the sample towards healthier, younger patients undergoing elective procedures.

Click to read the study in Annals of Surgery

Relevant Reading: Rehospitalizations among patients in the Medicare fee-for-service program

In-Depth [retrospective cohort]: This study enrolled 162,159 surgical patients whose records were collected by American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) in 2011. Patients undergoing general, upper GI, hepatopancreatobiliary, small and large intestine, vascular and thoracic procedures were included in the analysis. Because the ACS-NSQIP records 30-day readmission rates with respect to the index procedure rather than the discharge date, participants with length of hospital stay lasting longer than 10 days were excluded. This avoided possible cases with post-procedure LOS close to 30-days, with quick post-discharge readmissions missed by the ACS-NSQIP. Hospital stay over 10 days was associated with significantly increased rates of complications (65% vs. 10.5%), mortality (3.25% vs. 0.45%) and readmission (16.1% vs. 7.8%). The risk of 30-day readmission rate varied with the type of surgery and within each surgical subspecialty, but overall was 7.8%. Readmission was correlated with patient ASA class and specific comorbidities. Patients transferred from an outside hospital, patients with postoperative complications and those with longer LOS had an increased rate of readmission. Iterative multivariable regression established that ASA class and LOS were the most significant predictors of readmission. These two variables were used to create a predictive readmission score, which was validated using a smaller random cohort from the same population.

By Asya Ofshteyn and Allen Ho

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