Breakpoints

CLSI breakpoints or EUCAST breakpoints, applied consistently and re-runnable

A breakpoint revision can move a susceptibility rate by several points without one organism behaving differently. If your report cannot say which version it used, it cannot explain its own trend.

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Short answer

Breakpoints are the MIC or zone diameter values that separate susceptible from resistant. CLSI publishes the set used by most United States laboratories, EUCAST the set used across most of Europe, and the two do not always agree. Both revise their tables, so the same isolate can be reported differently in different years.

Computed from your own isolates, never from a national average.

Why a revision looks like a resistance trend

When a breakpoint is lowered, isolates that used to be reported susceptible are reported intermediate or resistant. The organisms did not change; the threshold did. A cumulative antibiogram that spans the revision will show a step, and unless the report carries its breakpoint version the step will be read as an epidemiological finding.

This is the strongest argument for keeping raw MIC values in the export rather than only the interpretation. With MICs you can re-run the year under the new table and see the real comparison.

What we do with the interpretation your laboratory reported

By default we use it. Your laboratory is the authority on its own results, its instrument, its verification and its reporting rules, and overriding that silently would be wrong.

Where MIC values are present, reinterpretation against a chosen CLSI or EUCAST version is available on the Stewardship plan and above, and the version used is named on the output. You can produce both and compare, which is usually more informative than either alone.

Reported interpretation, exactly as your laboratory issued it
Reinterpreted from MIC against a selected CLSI version
Reinterpreted from MIC against a selected EUCAST version
The version and the date stamped onto every export

Intermediate, and the awkward third column

EUCAST redefined intermediate as susceptible at increased exposure, which is a statement about dosing rather than a middle ground. CLSI introduced susceptible-dose-dependent for specific organism and drug pairs, which makes the same point differently. Neither definition survives being averaged into a single percentage without a note.

The builder therefore treats intermediate as a switch: excluded from the denominator by default, counted as resistant on request, and the choice is printed under the matrix.

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Every plan and limit is published, with no demo call.

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The builder runs on a synthetic sample dataset, or on your own CSV, parsed in your browser.

Questions

On this page's topic

Which breakpoint set should we report on?

The one your laboratory uses, so your antibiogram matches your reports. Reinterpretation is a comparison exercise, not a replacement for your laboratory's validated method.

Do you ship the full breakpoint tables?

Breakpoint tables are published and revised by CLSI and EUCAST, and using them is subject to their terms. A plan that includes reinterpretation includes the mapping work; we do not redistribute their documents.

What if my export has no MIC values?

Everything still works from the S, I and R interpretation. Only reinterpretation needs MICs.

See your own resistance picture, cut the way you actually work

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