Rediscovering Quality Control Methods for Health Care Improvement

• Activity Number: 193
• Type: Contributed
• Date/Time: Monday, August 10, 2015 : 10:30 AM to 12:20 PM
• Sponsor: Biometrics Section
• Author(s): Michele Shaffer* and Lori Rutman
• Companies: University of Washington and Seattle Children's Research Institute and University of Washington and Seattle Children's Hospital
• Keywords: Statistical process control ; quality improvement

Abstract

Studies of quality improvement (QI) are increasingly important as we build learning healthcare systems. QI studies frequently involve intense monitoring efforts over time. Aggregating data into pre-post analyses ignores a substantial proportion of the temporal component of these studies, and can lead to inappropriate findings. While uncommon in traditional biomedical research, statistical process control (SPC) methods are readily applicable and increasingly used for such studies. The SPC approach is highly visual, allowing inspection of the ongoing time series. We illustrate the benefit of SPC methods using asthma improvement efforts conducted at Seattle Children's Hospital. An SPC chart of asthma admissions showed a four-month increase in the post-intervention period was not temporally related to the intervention. Further investigation found the increase correlated with poorer local air quality due to extensive wildfires. Performing pre-post analysis with the same data would have erroneously demonstrated a highly significant increase (p< 0.0001) in admissions in the post-intervention group.