What Is a Cut-off?
Direct answer: A cut-off is the analyte concentration threshold that separates a positive (reactive) result from a negative (non-reactive) result. Samples at or above the cut-off read positive; below it, negative.
How a cut-off works
- The test is designed so the visible line appears only when the analyte concentration reaches the cut-off.
- Example: a THC urine test with a 50 ng/mL cut-off is positive only when THC metabolite is ≥ 50 ng/mL.
- Cut-offs are set per analyte and often align with regulatory standards (e.g., SAMHSA-style workplace thresholds).
The sensitivity/specificity trade-off
The cut-off balances two kinds of error:
- Lower cut-off — catches more true cases (higher sensitivity) but more false positives.
- Higher cut-off — fewer false positives (higher specificity) but more false negatives.
Buyers must confirm the cut-off matches the intended use — a screening cut-off differs from a confirmation threshold.
Why it matters
The cut-off determines the test's clinical meaning. A "positive" is only meaningful relative to its threshold, which is why cut-off values appear on datasheets and why regulatory programs specify them.
Frequently Asked Questions
What is a cut-off value? The analyte concentration threshold that separates positive from negative results.
Can a cut-off be changed? Yes — OEM/ODM formulations can be customized to a target cut-off for a specific market or program.
Does a lower cut-off mean a better test? Not necessarily — it trades sensitivity against specificity, so the right cut-off depends on the intended use.
Related knowledge
References
- CLSI guidance on establishing diagnostic test cutoff values.
By Progene Bio Regulatory Affairs Team · Medical Device QA · Medical disclaimer · Last reviewed: 2026-09-12