Six Sigma Method


The Six Sigma method is a strategy used in quality management and improvement. Six Sigma is used to identify flaws and reduce errors and discrepancies in production processes.[1] Initially introduced in 1987 at Motorola by Bill Smith, the methodology has been used in several manufacturing industries and later applied to healthcare.[2] Since Six Sigma can streamline procedures in healthcare, it has been shown to improve patient care by reducing costs, medical errors, and wait times.[3]

This methodology has been shown to prevent falls and injuries and decrease adverse medical events such as infection rates.

Six Sigma consists of 2 primary improvement methodologies depending on the use case: Six Sigma DMAIC and Six Sigma DMADV. The term's name is derived from the significant steps in the process, and the last two steps vary depending on which method is used. Each term's name is derived from the important steps in each process, but each is used for a different purpose.

  • DMAIC (define, measure, analyze, improve, control) is used to correct/improve an existing process, product, or service.
  • DMADV (define, measure, analyze, design, validate) is used to design a new process, product, or service.

Six Sigma methodology, DMAIC, to improve an existing process follows the five basic steps or phases of Define, Measure, Analyze, Improve, and Control to reduce errors, inefficiencies, and process variability.[4]

In the define phase, problems and issues within the process are outlined from both the business and client perspectives. This may include launching a team, gathering information, planning the project, and setting goals. For example, a project may define a medical error the organization wants to address. During the measure phase, further narrowing of the project focus occurs, and baseline data are collected. In the analyze phase, data are examined to help identify the root cause of an issue and help remove inefficiencies.

The improve phase establishes ways to improve the process and correct deficits. The improve phase may include solution brainstorming, evaluation, and optimization, as well as an implementation plan. Finally, the control phase provides monitoring and maintenance of the solution. Furthermore, the control phase often involves validating the project benefits and improving error rates.[1] Six Sigma is often used together with Lean Six Sigma, which reduces waste in a process.[3]

Six Sigma relates to the Greek letter Sigma, used to denote a standard deviation from the mean.[5] Thus, to reach Six Sigma, error rates are less than 3.4 defects in 1 million. Error rate or Defects per Million Opportunity (DPMO) is calculated before and after the intervention is enacted using the Six Sigma methodology to determine the effectiveness.[6] Some quantitative methods used in Six Sigma projects may include mathematical modeling, control charts, or analysis of variance (ANOVA).[7]

A control chart may show the change in outcomes over a period, while ANOVA can show the difference in outcomes between groups.[8]

Issues of Concern

Several quality improvement studies have shown issues of concern when implementing the Six Sigma methodology in healthcare. These issues of concern include the various challenges with Six Sigma implementation, the lack of studies about the actual success rates and costs of Six Sigma, and the unique aspects of healthcare as an industry. Execution of a Six Sigma project requires comprehensive planning, training, funds, and time. Studies have shown that a dedicated employee is needed to oversee a Six Sigma project.

Six Sigma methodology has several “belts” or tiers of project leader training. Depending on the training program, the designated levels or belts are as follows: white, yellow, green, black, and master black belt. White belts have the basic grounding and overview of Six Sigma. Yellow belts have 1 to 2 days of training and may assist those at higher belt levels or be assigned as contributing team members to a project. A green belt works part-time on Six Sigma projects and has 1 to 2 weeks of training. A black belt has at least two weeks of training and is a full-time manager of Six Sigma projects. While a Master Black Belt has supervised several projects and mentors those with green or black belts.[3]

For successful implementation, often, the project will need to include specific outcomes desired, a timeline, and any problems that may arise with implementation. Lastly, Six Sigma project implementation and the completion of the 5 phases may take 18 to 24 months or longer, making it difficult to implement solutions quickly.[5]

Studies have also shown that more research is needed due to limited evidence of Six Sigma being implemented correctly in healthcare systems.[6] Specifically, there are only a few examples of unsuccessful implementation of Six Sigma, and few studies show failures. Thus, the literature may not show the success and failure rates of applying Six Sigma in a healthcare setting. The DelliFraine et al. study concluded that further investigation is needed, including more in-depth design systems and comprehensive statistics. This would provide a better understanding of the full scope of Six Sigma project costs and its success in reducing errors, inefficiencies, and costs in healthcare.[6]

Lastly, an issue of concern is healthcare being a complex industry sector. Several aspects that make healthcare a more complex industry include the high level of service and the wide product range necessary in healthcare. Variability among the products and services clinicians choose for patients based on the patient’s personalized needs exists.[9]

Furthermore, the hospital staff is not trained the same as manufacturing workers. Instead, healthcare workers must often provide exceptional and personalized medical care depending on the patient’s illness and needs. Personalized care coupled with a diverse range of services required to deliver the end product or the necessary patient care in the hospital may affect the use of Six Sigma execution.

For example, two patients with the same diagnosis may have different treatment plans, including different surgeries or medications administered. Also, a patient may have preexisting conditions, such as the need for insulin therapy, making care for another health condition more complicated. With hospital healthcare, there is complexity regarding various critical and life-threatening aspects of patient care and the products needed, which does not allow for precise planning in hospital logistics.[10]

Therefore, this may require different management and planning than other industries when discussing supply chain aspects. The outputs of the services in hospitals are typically not tangible products but are patients. Thus, metrics are not always as easy to apply to the processes as they would be in manufacturing. These healthcare features lead to concerns regarding the execution of Six Sigma projects in healthcare. Some studies have proposed using an index in Six Sigma healthcare projects that may bridge the gap between the critical items that may present in healthcare while still being able to implement Six Sigma methodology in problem management.[10]

Clinical Significance

With the increased strain on the medical system worldwide and since Six Sigma is a successful management method in manufacturing, the use of Six Sigma may be beneficial to address the growing issues in healthcare. Evidence-based medicine (EBM) has been the basis for many quality improvement projects, including those executed with Six Sigma.[11] Most medical systems have seen an increase in patient numbers and the complexity of patient needs, while limited healthcare resources may exist.[1]

An increase in patient wait times and a decrease in patient satisfaction have occurred in multiple medical settings.[12] Furthermore, medical errors account for many deaths in the United States. According to Anderson and Abrahamson, up to 251,000 deaths in the United States annually can be attributed to medical errors. This would make medical errors the third leading cause of death.[13]

Since Six Sigma focuses on reducing errors and service variability, contributing to process efficiency, its use has improved hospital and outpatient organizational effectiveness.

Studies in the literature utilizing Six Sigma have shown to reduce inpatient length of stay and improve patient satisfaction.[14] Six Sigma has been used in various outpatient, inpatient, and nursing home models. In one study, the rate of Cesarean section deliveries decreased from 41.83% to 32%.[15]

Using Six Sigma in hip fracture surgery resulted in improved timely surgical care, better detection of complications, and reduced resource consumption with shorter lengths of stay and lower hospital costs.[16] In a study of patients with end-stage renal disease, the use of the Six Sigma methodology showed a reduction in the incidence of depression and anxiety in patients at discharge.[4]

The use of Six Sigma techniques in an ophthalmology outpatient setting demonstrated a reduction in the duration and variability of time spent by patients at the clinic. The clinic’s service capacity was also increased.[1] A nursing home study showed that using Six Sigma led to an increase in patient capacity without an increase in staff and an improvement in charting congruence.[3]

Six Sigma has also been shown to increase the rate patients receive primary care preventative services; in 2 clinics studied, one had a rate of 16.3% versus 100% in the Six Sigma method clinic.[17] Specifically, the application of Six Sigma in nursing has resulted in error reductions in several aspects of patient care, such as continuous IV infusions, insulin administration, protocols involving narcotics, and the handling of patient laboratory specimens.[18]

Overall, the Six Sigma method can be a powerful tool in reducing medical errors and medical costs while enhancing patient safety.

Nursing, Allied Health, and Interprofessional Team Interventions

The role of the interprofessional team is vital to successful quality improvement projects in which the Six Sigma methodology is used. Clinicians, nursing staff, allied health, and other interprofessional healthcare team members must be included in the Six Sigma initiatives and team goals set.

One outcome of a comprehensively planned Six Sigma project should be to foster the collaboration of multidisciplinary teams in the healthcare facility. Strong interprofessional relationships and knowledge of Six Sigma among team members would allow for better communication, enhanced patient care, and better analysis of the root causes of the problem, ultimately resulting in better solutions and outcomes. 

Research to detail the current organizational dynamic and flow, an assessment of what is successful within the organization, and an analysis of where improvements can and should be made determine the scope and steps of the quality improvement project. Part of the initiative's success is the involvement of the interprofessional team during the define phase of DMAIC. Hence, the entire system is assessed, and better decisions can be made regarding which interventions should be prioritized.

Various team members are critical in the subsequent steps after the projects have been defined, such as in the evidence-based planning and development of the initiatives. Specific outcomes of Six Sigma projects can be accomplished through benchmarking and setting distinct goals. Reasonable timeframes should be set to achieve the specified goals. Overall, part of the success of healthcare Six Sigma projects has been in studying the dynamics and interactions between interprofessional teams as team members work on interventions that have been shown to improve patient outcomes and care.

Nursing, Allied Health, and Interprofessional Team Monitoring

In the last phase of a Six Sigma project, the control phase, the project management team monitors how the Six Sigma solution affects the interprofessional teams and patient outcomes and care. The monitoring is tailored to the goals of the project and the root causes identified. The control phase may monitor care delivered by specific team members such as physicians, nurses, lab technicians, or any other healthcare team member. However, a Six Sigma project may involve several teams and various aspects of patient care. In these projects, the solutions and the processes to achieve those solutions are monitored more holistically to verify the project's success.

Significant components of any quality assurance project are reducing error rates to enhance patient safety and improving patient care. Six Sigma is a method used to set the standard of zero errors, and Six Sigma limits are 3.4 errors per million events. The five main steps of a DMAIC Six Sigma project used to improve an existing process or service are to define, measure, analyze, improve, and control. With the use of DMAIC, the root causes of errors and deficiencies in patient care can be determined; process improvement strategies can then be executed.

Article Details

Article Author

Masha Ilin

Article Editor:

Julie Bohlen


1/9/2023 11:33:56 AM



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