Laboratory quality indicators are commonly measured as averages or percentages. For example:
- The turnaround time (TAT) for a sendout test averages 3.5 days.
- Type O units are available 99.9% of the time in an emergency release.
In the first example, it might appears that 3.5 days is a reasonable TAT for a sendout test at first glance, but an average of 3.5 days means the result can be available anytime between the same day to a week later. A patient may have to schedule an appointment at least one week later to ensure the result is available. This may potentially delay treatment. As for the physicians, they want to know when their patients' results will come back; they are not interested in knowing the average but exactly when the result will be available.
In the second example, 99.9% might sound impressive but it would translated into 1 out of every 1000 patients requiring emergency transfusion being at risk of ABO hemolytic reaction. In fact if 99.9% is used to measured quality of the processes that happened in our everyday life, that would translate into:
- 18 plane crashes daily
- 17,660 mail mix-ups hourly
- 3,700 medication errors daily
- 10 dropped babies daily
- $24.8 million worth of incorrect charges hourly
- 500 wrong procedures performed weekly.
Other industries realized long ago that measuring quality based on percentage or average is not adequate to satisfy the customers. The need for a higher standard of quality led to the use of Six-Sigma.