Most people who work in hospitals are familiar with the terms “Six Sigma” and “Lean.” Lean (L) was developed by Toyota and is a program of cost and waste reduction while maintaining quality. According to the folks at Motorola University, Six Sigma is a “metric*, a methodology and a management system.” Specifically, Six Sigma (SS) refers to six standard deviations from the mean or in the case of manufacturing, an attempt to achieve fewer than 3.4 defects for every one million opportunities.
Since 1999, these two tools have been adopted by many healthcare organizations. But despite more than 10 years’ experience, evidence of improved outcomes based on re-engineering of processes using SS/L is lacking according to a recent review of the healthcare literature on the subject.
The authors looked at 177 medical articles on SS/L published in the last 10 years. Only 34 papers reported any outcome data at all and of these, two-thirds did not provide any statistical analyses to justify their results. The methods used in these reports were judged to be of low scientific quality. Only three papers focused on clinical topics.
I asked the lead author of the review, Jami DelliFraine, whether she had expected to find favorable results in the literature on SS/L. She said, “I suspected that I would find a positive association between better processes/outcomes and the use of SS/L.” Thus, an author with a predisposition in favor of SS/L reported negative results in her review of the subject. I also questioned her about the cost of training personnel and she answered, “It is very expensive to implement these programs and train people for these programs.”
The proponents of SS/L must respond to the challenge and in the era of evidence-based medicine, produce some proof that the investment in time, money and personnel in SS/L will yield significant improvements in quality.
Finally, it is hard to resist a jab at SS/L via the Lean pioneers and Dr. Berwick’s example of what medicine should aspire to, Toyota, which has recalled some 9 million vehicles in the last 10 months. Using SS and taking the position that a defective vehicle represents one opportunity, Toyota would have to manufacture 3.4 billion consecutive flawless vehicles to achieve a rate of 3.4 defects per million. Guddorakku (Good luck).
*A metric is any number that you can put in a box in a computerized nursing record, and in turn be chewed over by a second layer of bureaucrats, resulting in a another number used to beat physicians over the head.