Use when
- Von Frey responses are collected with an up-down sequence.
- The response/no-response series and starting force are recorded.
- The analysis needs an auditable threshold estimate.
Data Analysis
Data analysis
Up-down threshold method
The up-down method estimates mechanical withdrawal threshold from a response sequence rather than a single force value.
Decision summary
Use the up-down method when the protocol follows a valid response-sequence design and the raw sequence can be audited. Do not treat the calculated threshold as independent of the scoring rule that produced it.
| Input | Stimulus sequence and response/no-response events. |
|---|---|
| Output | Estimated 50 percent withdrawal threshold or equivalent threshold estimate. |
| Assumption | Response probability changes monotonically across the stimulus series. |
| Audit field | Starting force, sequence, step rule, cutoff, and excluded trials. |
Do not use when
- The protocol used fixed-force testing or a non-sequential response curve.
- Raw response sequence, step size, or cutoff handling is missing.
Caveats
- The method estimates a threshold from a defined sequence, not a directly observed single value.
- Protocol deviations can invalidate the calculation.
- Different filament sets or electronic force ramps require clear method notes.
Reporting checklist
- Report starting stimulus and step logic.
- Report complete response sequence.
- State calculation method and cutoff rules.
- Report excluded or ambiguous responses.
- Keep raw data available alongside derived threshold.
References
Chaplan et al. 1994. Quantitative assessment of tactile allodynia in the rat paw.
Source for a widely used up-down threshold approach in von Frey testing.
https://pubmed.ncbi.nlm.nih.gov/7990513/
Dixon 1980. Efficient analysis of experimental observations.
Statistical background for up-down experimental designs.
https://pubmed.ncbi.nlm.nih.gov/7383457/
Related surfaces
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