title: Control charts in healthcare quality improvement. A systematic review on adherence to methodological criteria.
abstract: OBJECTIVE
  Use of Shewhart control charts in quality improvement (QI) initiatives is increasing. These charts are typically used in one or more phases of the Plan Do Study Act (PDSA) cycle to monitor summaries of process and outcome data, abstracted from clinical information systems, over time. We summarize methodological criteria of Shewhart control charts and investigate adherence of published QI studies to these criteria.
  
  
  METHODS
  We searched Medline, Embase and CINAHL for studies using Shewhart control charts in QI processes in direct patient care. We extracted methodological criteria for Shewhart control charts, and for the use of these charts in PDSA cycles, from textbooks and methodological literature.
  
  
  RESULTS
  We included 34 studies, presenting 64 control charts of which 40 control charts plotted two phases of the PDSA cycle. The criterion to use 10-35 data points in a control chart was least adhered to (48.4% non-adherence). Other criteria were: transformation of the data in case of a skewed distribution (43.7% non adherence), when comparing data from two phases of the PDSA cycle the Plan phase (the first phase) needs to be stable (40.0% non-adherence), using a maximum of four different rules to detect special cause variation (14.1% non-adherence), and setting control limits at three standard deviations from the mean (all control charts adhered).
  
  
  CONCLUSIONS
  There is room for improvement with regard to the methodological construction of Shewhart control charts used in QI processes. Higher adherence to all methodological criteria will decrease the risk of incorrect conclusions about the process being monitored.
authors.affiliation: Antonie Koetsier, MSc, Dept. of Medical Informatics, Academic Medical Center, Room J1b-115-2, P.O. Box 22700, 1100 DE Amsterdam, The Netherlands. a.koetsier@amc.uva.nl
authors.forename: A
authors.initials: A
authors.lastname: Koetsier
authors.forename: S N
authors.initials: SN
authors.lastname: van der Veer
authors.forename: K J
authors.initials: KJ
authors.lastname: Jager
authors.forename: N
authors.initials: N
authors.lastname: Peek
authors.forename: N F
authors.initials: NF
authors.lastname: de Keizer
mesh_terms: D019295:Computational Biology; D017598:Efficiency, Organizational; D006801:Humans; D017146:Models, Organizational; D058996:Quality Improvement; D011787:Quality of Health Care; D012306:Risk