Use of statistical process control charts in stroke medicine to determine if clinical evidence and changes in service delivery were associated with improvements in the quality of care

Background and objective: Monitoring the effect of service changes on quality of care is essential. By using statistical process control (SPC) charts, this study aimed to explore the relationship between changes in the structure of stroke services and the process of care.

Methods: Prospectively acquired data on the process of acute stroke care from three hospitals admitting 2962 patients (July 2001 to June 2004) were charted retrospectively on SPC charts for individual values (I charts) to determine whether or not "special cause variation'' followed known changes in stroke service structure and publication of the Medical Research Council (MRC) Heart Protection Study. Unexpected signals of special cause variation were identified and reasons for observed patterns were sought by discussion with clinical teams.

Results: Improved brain imaging provision was followed by a reduction in time to imaging and earlier prescription of aspirin for ischaemic stroke. The MRC Heart Protection Study was followed by increased statin prescription. However, increasing beds allocated to stroke had no influence on the proportion of patients receiving stroke unit care. Some unexpected signals of special cause variation could be plausibly explained (eg, breakdown of brain scanner), but others could not. Anecdotal evidence from healthcare professionals suggests that charts may be acceptable in clinical practice.

Conclusion: SPC charts have the potential to provide valuable insights into the impact of changes in structure of services and of clinical evidence on the process of stroke care. In the present study, the charts were generally well received by healthcare professionals.