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Pediatr Qual Saf. 2019 Sep 17;4(5):e216. doi: 10.1097/pq9.0000000000000216. eCollection 2019 Sep-Oct.

Addressing Challenges of Baseline Variability in the Clinical Setting: Lessons from an Emergency Department.

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Department of Pediatrics, George Washington School of Medicine and Health Sciences, Washington, D.C.
Division of Emergency Medicine, Children's National Health Systems, Washington, D.C.
Associates in Process Improvement, Austin, Tex.


To demonstrate methods of adjusting data in quality improvement projects for better learning about interventions over time.


A secondary analysis of data from a quality improvement project to improve patient wait times at an urban academic pediatric emergency department using electronic medical data from 2015 to 2018. The primary outcome was the wait times for low-acuity patients. Control charts were used to determine if the interventions were effective in reducing wait times. Two different data adjustment techniques were applied to account for changes in patient volume and seasonal effects on the outcome measure.


We more effectively demonstrated improved patient wait times after adjusting for patient volume or seasonality. Patient wait times decreased from 75.2 to 72.9 minutes after the intervention; a 3% decrease sustained over 18 months. A strong correlation between patient volume and wait times was noted. Process stability was achieved on the control charts after data adjustment, with one centerline shift after data adjustment in contrast to 5 centerline shifts required before data adjustment.


Adjusting for seasonality or patient volume created process stability and improved learning from control charts. After adjustment, we sustained decreased patient wait times more than a year out from the original intervention Adjusting by patient volume seems to be a preferred method of adjustment. Our findings support the importance of adjusting for baseline variability affected by seasonality or patient volumes, especially in flow projects, as a high yield method for process improvement.

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