Pareto (1848-1923), was an Italian economist, and is famous for having introduced the concept of the 80/20 rule, the concept that 80% of effects are governed by just 20% of the causes. I am a big believer in the 80/20 rule, although the ratio is of course an arbitrary one.

How can Pareto’s law/rule/principle apply to the microbiology laboratory?

For example, one could postulate that:

• 80% of complaints come from 20% of laboratory users.
• 80% of ideas for lab innovations come from 20% of the staff.
• 80% of laboratory errors actually negatively affect the patients 20% of the time.

Maybe 80/20 is a bit optimistic… Critics of Pareto’s law have quoted that 90/10 may be a more realistic ratio.

However the one area that interests me most with regards to this topic is the percentage of microbiology samples that have clinical benefit to the patient. Do 80% of changes to patient management (I.e. clinical benefit) come from 20% of the samples? Probably an overestimate in my opinion. I would say that about 90-95% of clinical benefit come from about 5-10% of the samples…

It is the 90% of samples that are unlikely to have a clinical benefit that I am really interested in. Can we predict which samples these are likely to be? Why are they sent in the first place? Can education and good gatekeeping reduce this percentage? (I passionately believe so.) Can we redirect/reallocate testing and test budgets into areas where there is more likely to be a change in patient management from the result? For me this should be one of the principal aspirations of any microbiology laboratory.

The stronger the links are between the laboratory and its users, the more likely it is that you will have success in altering Pareto’s ratios…

Michael