Understand the relationship
The reasoning behind the result
Titre is a reciprocal dilution, not a concentration
The endpoint convention uses the highest dilution that still meets the assay's defined response criterion. A reciprocal value of 400 describes a 1:400 dilution. It does not directly measure antibody mass or concentration.
This tool starts after the assay has classified each replicate. It applies your entered fraction rule to those counts rather than choosing a signal cutoff or interpreting an instrument reading.
The tested range can bound the answer
When the last tested dilution still qualifies, the record establishes only that the endpoint is at least that dilution. When no tested dilution qualifies, the endpoint is below the first tested dilution under the entered rule. Neither case supplies an exact untested value.
A qualifying dilution followed by a nonqualifying dilution gives a recorded endpoint at the last qualifying tested step. The true transition may lie between tested steps; interpolation is not performed.
Preserve irregular patterns
If a nonqualifying dilution is followed by a qualifying one at a higher dilution, the pattern is nonmonotonic. The tool displays the highest observed qualifying step but labels the inconsistency instead of presenting an ordinary endpoint conclusion.
Experimental interference, variability or recording problems require method-specific review. No cause, clinical meaning, treatment implication or significance threshold is inferred from this record.
Follow the numbers
A bounded reciprocal titre of 400
- At the 100% replicate rule, 2/2 qualifies and 0/2 does not.
- Dilutions 1:100, 1:200 and 1:400 qualify; 1:800 does not.
- The highest qualifying tested dilution is 1:400, and the next tested dilution bounds it above.
Report the recorded reciprocal titre as 400 with its tested dilution series and rule; no concentration or clinical interpretation follows.
Quick guide
How to use this calculator
- Enter the positivity rule for replicates from the actual method.
- Enter recorded positive and tested counts at each dilution.
- Read the highest qualifying dilution together with its bound and monotonicity status.
- Retain the original record; this calculation does not diagnose a condition or compare assay methods.
Calculation method
Calculation and interpretation
Summarize an entered dilution-response record without inventing a biological or diagnostic threshold.
Qualifiesᵢ = positiveᵢ/testedᵢ ≥ entered rule; recorded titre = greatest qualifying reciprocal dilution
Worked example
A bounded reciprocal titre of 400
Report the recorded reciprocal titre as 400 with its tested dilution series and rule; no concentration or clinical interpretation follows.
Qualifiesᵢ = positiveᵢ/testedᵢ ≥ entered rule; recorded titre = greatest qualifying reciprocal dilution
Supported inputs
Precision and limits
An entered laboratory plan
This tool reconciles the measurements and choices you enter. It does not select a biological protocol, certify a preparation, assess sample suitability or establish an equipment operating limit.
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