Many lives could be saved if a simple mathematical technique used since the 1920s to check quality control in car manufacture is applied to the performance results of hospitals, says a British team.
The approach could easily have picked up a clear excess of childhood deaths after heart surgery at the Bristol Royal Infirmary in 1997, a year before problems were identified, says Tom Marshall of the University of Birmingham.
It could also have highlighted the high number of deaths among the elderly women patients of Harold Shipman, the former British doctor and now convicted serial killer.
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But the UK Department of Health鈥檚 argues that while the technique is widely used in industry, it may be too simplistic for use with hospital data: 鈥淭he very simplicity of the technique鈥檚 approach and application means it may not be the best technique to apply universally within the more complex environment of the NHS.鈥�
The DoH accepts the article raises important issues and adds: 鈥淲ork is already underway to set up a new national mandatory system for reporting and analysing adverse health care events.鈥�
The graphical method was developed by US physicist Walter Shewhart for use in the manufacturing industry. Scores are not ranked into a league table. Instead, the number of adverse outcomes is plotted against the total number of cases on a graph.
A line is drawn through the mean, and all scores within three standard deviations (in practice, most of the scores) are considered to be down to inherent variation in the system. Any scores outside the 鈥榗ontrol limits鈥� suggest a special cause.
鈥淭his tells you where the real problems in a system are,鈥� Marshall told 快猫短视频. 鈥淚n a league table, someone has to be at the top and someone has to be at the bottom, but that doesn鈥檛 necessarily mean any kind of intervention should be taken.
鈥淭his technique has a huge number of applications 鈥� for hospitals, schools, universities, as well as manufacturing,鈥� he says.
Marshall鈥檚 team completed case studies on six sets of data using the control charts, including the data on mortality rates of women aged over 65 in Shipman鈥檚 area. This would not routinely be analysed, notes Marshall.
鈥淏ut the data on Bristol Infirmary cardiac surgery was available in 1997 to some very eminent people, yet using conventional statistical approaches they were unable to conclude that there was a case for intervening. The control chart approach gives you a very clear answer: there was,鈥� Marshall says.
He thinks one of the key advantages of using the approach is that it makes it clear when not to intervene.
鈥淚ntervening when one particular team is not genuinely performing more poorly can make things worse,鈥� he says. 鈥淗it squads are often sent in to put pressure on schools at the bottom of league tables. But the truth is those schools might not be doing anything different.鈥�
Marshall thinks that decades of effective use in manufacturing proves the robustness of the approach. 鈥淚n the 1950s, the technique was taken to Japanese car manufacturers, who were producing pretty poor quality cars. They were told that if they adopted this approach, they鈥檇 be beating the world in two to three decades. The rest is history.鈥�
More at: The Lancet (vol 357, p 463)