Paired HAI Titer Rise
Compare paired HAI reciprocal titers against a caller-defined rise criterion; does not establish acute infection independently.
Description
Compare acute and convalescent reciprocal HAI titers and flag whether their ratio meets a supplied fold-rise criterion.
Hemagglutination inhibition, abbreviated HAI or HI, measures a specimen’s ability to inhibit virus-mediated red-cell agglutination under an assay protocol. Titers are commonly recorded as reciprocal dilutions: a reported titer of 80 represents a 1:80 dilution endpoint. Paired specimens allow the later result to be compared with an earlier result.1
A fold rise is the later reciprocal titer divided by the earlier reciprocal titer. Comparing that ratio with a chosen criterion is an arithmetic summary, whose interpretation still depends on specimen timing, assay conditions, and the clinical or study context.
Paired HAI Titer Rise returns the ratio and a boolean comparison against the supplied criterion. No diagnostic cutoff is chosen automatically.
When to summarize a pair of HAI titers
Use the tool after comparable acute and convalescent results have been scored. Keep collection dates and any below-range or above-range assay notation with the pair.
- Calculate a fold change from two positive reciprocal titers.
- Apply a study-defined minimum fold-rise rule consistently.
- Check whether an exact-threshold result qualifies.
How to enter paired titers and evaluate the rise criterion
- Enter Acute reciprocal titer and Convalescent reciprocal titer as positive numbers, such as 20 and 80 rather than 0.05 and 0.0125.
- Enter a positive Minimum fold rise chosen for the analysis.
- Run the calculation and read Fold rise and Meets supplied rise criterion.
- Interpret the flag alongside assay comparability, specimen timing, and the source protocol.
foldRise = convalescentReciprocalTiter/acuteReciprocalTiter; meetsSuppliedRiseCriterion = foldRise ≥ minimumFoldRise The implementation performs one division and an inclusive comparison. A ratio exactly equal to the criterion returns true.
{
"input": {
"acuteReciprocalTiter": 20,
"convalescentReciprocalTiter": 80,
"minimumFoldRise": 4
},
"output": {
"foldRise": 4,
"meetsSuppliedRiseCriterion": true
}
}The tool accepts decreasing titers and returns a ratio below one. It requires only a positive criterion, so criteria below one are accepted too; that may not represent a rise. It does not enforce integer titers or a twofold dilution grid. Zero titers, nonpositive criteria, and nonfinite inputs are rejected.
Limitations of a paired-titer ratio
- The ratio alone does not establish acute infection, protection, or the cause of an antibody response.
- No assay variability, uncertainty interval, vaccination history, or specimen-timing assessment is included.
- Censored results such as less than 10 or greater than 640 cannot be entered as inequality strings. A substituted number would create a point ratio with different meaning.
- The supplied minimum is not verified against a laboratory or clinical protocol, and a true flag states only that the arithmetic comparison passed.
Alternative or Complementary antibody and agglutination endpoints
A PRNT endpoint summarizes plaque reduction across dilutions rather than a paired HAI ratio. A hemagglutination endpoint scores agglutination itself, which is a distinct measurement from antibody-mediated inhibition.
References
-
Manual for the laboratory diagnosis and virological surveillance of influenza — World Health Organization (2011)
Similar or alternative tools
- PRNT Dilution Endpoint
Find the highest tested reciprocal dilution meeting a plaque-reduction criterion and retain censoring flags.
- Hemagglutination Dilution Endpoint
Summarize a positive hemagglutination dilution series; this is not an HAI antibody-rise calculation.