A case-control study of length of stay outliers

Inpatients with extended length of stay (LOS), referred to as LOS outliers, pose a challenge to health systems by contributing to high costs while assuming all the risks associated with hospital-acquired conditions. Limited research has been conducted within the US health system to better define LOS outliers and the risk factors for becoming an outlier in the setting of inpatient medicine stays.

This was a retrospective study on adult inpatient admissions to the general medicine service of a university hospital from September 2015 to August 2016. Cases were defined as patients with observed LOS 3 SD above predicted. Controls were defined as those who stayed within 3 SD of predicted LOS.

A total of 108 LOS outliers were identified through the University Health System Consortium, and 72 were matched with inlier controls by principal diagnosis and disease severity.

Compared with their inlier controls, outliers stayed 32.41 days longer and cost $77,228 more per stay. There were higher odds of being an outlier observed for patients with a history of smoking (odds ratio [OR], 29.5; 95% CI, 2.9-301.3), in-hospital complications (OR, 17.6; 95% CI, 3.5-88.6), hospital-acquired infections (OR, 7.2; 95% CI, 1.7-31.4), and discharge to a facility (OR, 11.5; 95% CI, 2.6-50.0).

In-hospital complications, hospital-acquired infections, and discharge to a facility are all predictors of not only increasing hospital days for patients but also increasing the risk of becoming LOS outliers, who stay disproportionately longer and use disproportionately more resources than predicted.