Abstract
Background
Unplanned hospital admission after intended outpatient surgery is an undesirable outcome.
We aimed to develop a prediction model that estimates a patient’s risk of conversion
from outpatient surgery to inpatient hospitalization.
Methods
This was a retrospective analysis using the American College of Surgeons National
Surgical Quality Improvement Program database, 2005 to 2018. Conversion from outpatient
to inpatient surgery was defined as having outpatient surgery and >1 day hospital
stay. The Surgical Risk Preoperative Assessment System was developed using multiple
logistic regression on a training dataset (2005–2016) and compared to a model using
the 26 relevant variables in the American College of Surgeons National Surgical Quality
Improvement Program. The Surgical Risk Preoperative Assessment System was validated
using a testing dataset (2017–2018). Performance statistics and Hosmer-Lemeshow plots
were compared. Two high-risk definitions were compared: (1) the maximum Youden index,
and (2) the cohort above the tenth decile of risk on the Hosmer-Lemeshow plot. The
sensitivities, specificities, positive predictive values, negative predictive values,
and accuracies were compared.
Results
In all, 2,822,379 patients were included; 3.6% of patients unexpectedly converted
to inpatient. The 6-variable Surgical Risk Preoperative Assessment System model performed
comparably to the 26-variable American College of Surgeons National Surgical Quality
Improvement Program model (c-indices = 0.818 vs. 0.823; Brier scores = 0.0308 vs 0.0306,
respectively). The Surgical Risk Preoperative Assessment System performed well on
internal validation (c-index = 0.818, Brier score = 0.0341). The tenth decile of risk
definition had higher specificity, positive predictive values, and accuracy than the
maximum Youden index definition, while having lower sensitivity.
Conclusion
The Surgical Risk Preoperative Assessment System accurately predicted a patient’s
risk of unplanned outpatient-to-inpatient conversion. Patients at higher risk should
be considered for inpatient surgery, while lower risk patients could safely undergo
operations at ambulatory surgery centers.
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Article info
Publication history
Published online: February 22, 2022
Accepted:
January 16,
2022
Identification
Copyright
© 2022 Elsevier Inc. All rights reserved.