09.11.2024

When there are no breakpoints!

The first and very important question is, when are there no breakpoints in the EUCAST breakpoint tables?

Look for guidance on the interpretation of test results in breakpoint tables, expert rules and in EUCAST advice on expected phenotypes. In breakpoint tables guidance can be in the form of numerical values, a “dash” or “IE”. Elsewhere the recommendations are in tables describing the expected activity of agents against organisms.

So, when are there no EUCAST breakpoints?

1. When a species or an agent is not in any of the mentioned tables.
2. When a numerical breakpoint is substituted with an “IE”, eg. insufficient evidence to determine a breakpoint.

When are there EUCAST breakpoints?

1. A species/agent is listed in tables with numerical values.
2. A species/agent is listed with dash (“-“) in tables. The dash carries clear EUCAST advice that the agent is unsuitable for treatment of infections caused by the organism and to avoid clinical use (and testing). If there is a need to report, EUCAST advocates reporting as “resistant” without prior testing.
3. A species/agent is listed with guidance in either “Expert rules” or “Expected phenotypes”.

The clear difference between “dash” and “IE” is emphasized. “IE” is to some extent encouraging and if an MIC can be obtained, further advice may be available in “When there are no breakpoints”. “Dash”, on the other hand, relieves the microbiologist from having to discuss or act further.