Six Sigma Savings goes to the Dogs, Cats, Horses, etc.

Posted by Sten Westgard, MS

An online-first paper just came to our attention, a study that used Sigma-metrics and the Six Sigma Cost Worksheets included in our book:

Use of Six Sigma Worksheets for assessment of internal and external failure costs associated with candidate quality control rules for an ADVIA 120 hematology analyzer. Cian F¹, Villiers E, Archer J, Pitorri F, Freeman K. Vet Clin Pathol. 2014 Apr 21. doi: 10.1111/vcp.12141. [Epub ahead of print]

This new study applied Sigma-metrics to hematology tests, but used a different set of quality requirements more appropriate for veterinary uses. This is interesting to see, since the differences between the CLIA requirements for hematology (for humans) are sometimes half or a third of what is being used for veterinary uses (dogs, cats, etc.). So what might not be a great method for humans could be a world class method for dogs!

The authors estimated the savings for changing from 1:2s rule with N=3 (their current practice, and one with a high false rejection rate) just to the 1:2.5s rule with N=3. Even that slight change created a 72% reduction in QC usage, saving about £822 a year. That doesn't seem like much, admittedly, but this a lab with relatively small volume: about 30 CBCs a day, 9000 CBCs annually. That Six Sigma techniques can save money for the lower volume vet lab and the higher volume human reference lab is a good sign of universal utility.

This savings is also assuming that only control costs are taken into account - that even when rejections occur, no patients are re-run, only the controls. If the lab policy was to re-running all the patients whenever there was a rejection flag, the savings would be an order of magnitude higher.

Congrats to this veterinary lab, for applying a technique that many (human) labs are still lagging in adoption.