There has been an explosion of interest in patient safety in the last decade and a half (fig 1). Governments have responded to concerns over safety with major initiatives such as the formation of the Natural Patient Safety Agency for England and Wales. Here, we report on the results of a search for the most influential papers that have initiated and sustained this movement. We also invite readers to visit our website (see below) to nominate their own candidates for inclusion.

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Figure 1

 Growth of citation counts of papers coded in Medline under the terms “patient safety”, “quality in healthcare” and “medical/medication errors” from 1966 to 2005. Each graph was normalised by taking the data for the year 2005 as 100% (“patient safety” 2472; “quality in healthcare” 21 870; “medical/medication error” 7867).

METHODS

We set out, in the first instance, to identify studies that had been most influential in changing how people think and act in the context of patient safety. It was impossible to analyse and carry out citation counts on all potentially relevant articles as the number of papers indexed under “patient-safety” is vast, with over 2000 papers for the year 2005 alone. An initial list of papers that we judged influential was drawn from a systematic review of the patient-safety literature.¹ This was augmented by articles encountered by the authors in the course of their duties in directing the Patient Safety Research Programme for the Department of Health (England). A long list of 62 articles that appeared influential or important was drawn up, and a citation count (total and per year) was obtained for each article from the ISI Web of Science database. We also obtained citation counts using Google Scholar and Scopus. Correlations of rank order between the three citation counters were all close (>0.93).

The full listing of citation counts is provided in our paper “Patient safety—an unsystematic review and bibliography” available on the internet at http://www.pcpoh.bham.ac.uk/publichealth/psrp/PS_review.htm. As the articles selected were based on subjective personal selection, we have provided a facility for others to insert their favourite articles and to state why these have influenced them. Here, we provide an account of the top 10 most highly cited papers on the topic of patient safety (table 1), along with a few others that have not yet had time to accrue high citations, but are following a rapid upward trajectory. We classify papers into those describing the epidemiology of harm and error, those dealing with the underlying psychology and sociology, and those evaluating interventions to improve patient safety. In essence we cover three questions:

1. How common is the problem?

2. What are the underlying causes?

3. What can be done about it?

RESULTS

Epidemiology

Four of the top 10 papers describe the epidemiology of error in healthcare. The two most highly cited papers disseminated the results of the Harvard Medical Practice Study.^2,3 These were the first major studies to show that medical care causes a large number of injuries to patients, many of which are preventable. As a result of this study, Wilson et al⁴ conducted the Quality in Australian Health Care Study published in 1995, also in our list of the 10 most highly cited articles. Subsequent studies of this type, such as those by Vincent et al⁵ in the UK and Baker et al⁶ in Canada, are widely cited but do not make the top 10. However, a study completed by Bates et al⁷ in 1995 measured the incidence of adverse drug events of different types and showed that most medication errors occur at the drug-ordering stage.

Psychology and sociology

Two of our top 10 papers explore the cognitive basis of human error: “Models and management” by Reason⁸ and “Error in medicine” by Leape.⁹ These build on earlier work by Reason himself and the great Danish psychologist, Rasmussen, which show how errors can be classified—for example, into “skills-based” errors (slips that occur when attention is diverted from a task that is under sub-conscious control), “rule-based” errors (slips that occur when the wrong rule is chosen during problem solving) and “knowledge-based” errors (where a mistake occurs because of lack of knowledge or misinterpretation of a problem). Both Reason and Leape build on these insights to argue for an emphasis on systems failure and a less hierarchical healthcare culture, and this chimes with the work of Helmreich and Merritt in aviation,¹⁰ which has been hugely influential in medical research, even though it does not make the cut into the top 10. Likewise, the study by Friedman et al¹¹ on the effect of sleep loss on the performance of junior doctors has “spawned a dynasty” despite not quite making the top 10. However, the immensely influential paper by Fischhoff on the pervasive nature of what we would now call “hindsight bias” comes in at number five.¹² This has obvious relevance both for research and for safety practices, such as root cause analysis and confidential enquiries, which rely on retrospective judgements about the safety of care.

Interventions

Studies into interventions are less common than studies into the incidence and causes of medical errors, but three make the cut. A large body of patient safety literature exists on the effect of computer protocols and reminder systems, the most highly cited of which was the paper by McDonald.¹³ This article has had plenty of time to accrue citations, but two other top 10 papers from Bates et al¹⁴ and from Hunt et al¹⁵, both published in 1998, have registered even higher annual citation rates. Another important intervention that has been studied is the effect of reducing doctors’ working hours on the number of adverse events that occur in intensive care units. This study is a randomised trial by Landrigan et al¹⁶ It showed that the rate of serious errors can be reduced by more humane scheduling of junior doctors’ work hours. The study by Landrigan is too recent to make the top 10, but the paper has received 25 citations in <1 year.

DISCUSSION

Limitations to the study

The citation counters used did not permit us to determine the number of citations received by articles that were published in books. In consequence, some of the very important articles cited in our original paper may have been omitted from our hierarchy of most highly cited articles. Likewise, we fully concede that the selection of papers for citation analysis is subjective, which is why we invite readers to visit http://www.pcpoh.bham.ac.uk/publichealth/psrp/PS_review.htm to read the full text of our article and add their own opinions on the most important papers. In this way, we can all identify the intellectual heart of the patient safety movement and ultimately develop a consensus-based “reader in patient safety” analogous to similar reviews in health sociology.^17,18

A prize for patient safety research?

Who should be awarded the “Nobel prize” for safety research? On the basis of citations, there are two leading candidates, Lucian Leape and David Bates, each of whom contributed to three of the top 10 citation classics. James Reason is another contender, as he created many of the ideas we now take for granted in the safety movement. Perhaps we should award three prizes: Leape for measuring the size of the problem, Reason for understanding why there is such a problem and Bates for doing something about it. Once again, we invite readers’ views.