The p-control chart: a tool for care improvement

The p-chart is a user-friendly tool for monitoring adverse events. By converting data into knowledge, it is helpful in interpreting and reducing sources of variability in care. Certain basics for developing expertise to use p-charts correctly are necessary. This paper provides key elements on how to develop and interpret a p-chart for clinical practice, how to successfully integrate this tool within a comprehensive approach, and how to report a study based on p-chart utilization. The p-chart combines time series analysis with a graphical presentation of data by plotting successive indicator measurements in chronological order. The pragmatic choice of well-defined indicators to be monitored is essential. Exact control limits based on the binomial distribution and the incorporation of risk adjustment represent important contributions for further improving the tool's performance in health-care settings. The solution needed to reduce adverse events is not available from measurement alone. The success of routine introduction of the p-chart requires investigation of the causes of indicator variations and the trying out of quality improvement initiatives. It must be supported by strong management leadership within an atmosphere of constructive evaluation. The implementation of the p-chart into clinical practice encourages practitioners to continuously undertake a critical examination of the care delivered. Nearly a century after it was created in the manufacturing industry, the control chart now contributes to improving the quality of health-care processes and patient safety.