Ames Revertant Background Screen

Screen replicate Ames revertant counts against background with an explicit viability criterion; not a definitive mutagenicity determination.

Description

An Ames count screen compares treated revertants with background while preserving a viability gate.

An Ames count screen compares treated revertants with background while preserving a viability gate. A large count increase without adequate viability evidence is not automatically a valid positive screen.^[1]

Screen replicate Ames revertant counts against background with an explicit viability criterion; not a definitive mutagenicity determination.

When to use Ames Revertant Background Screen

Use this tool to screen replicate Ames revertant counts against background with an explicit viability criterion; not a definitive mutagenicity determination.

Prepare the sample, count, growth or assay measurements requested by this tool. Confirm units, sampling periods and reporting bases; supply independently established comparison criteria where requested.

How to use Ames Revertant Background Screen and understand its results

Prepare the sample, count, growth or assay measurements requested by this tool. Confirm units, sampling periods and reporting bases; supply independently established comparison criteria where requested.
Enter treatedRevertantCounts, controlRevertantCounts, minimumFoldIncrease, treatedViabilityFraction, minimumValidViability using the field table and calculation rules, then run the tool.
Read meanTreatedRevertants, meanControlRevertants, backgroundFoldIncrease, assayViabilityAdequate, screenFlag. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
treatedRevertantCounts	Treated revertant counts	list of number	Required
controlRevertantCounts	Control revertant counts	list of number	Required
minimumFoldIncrease	Minimum fold increase	number	Required
treatedViabilityFraction	Treated viability fraction	number; minimum: 0; maximum: 1	Required
minimumValidViability	Minimum valid viability	number; minimum: 0; maximum: 1	Required

Enter nonempty replicate lists of nonnegative integer treated/control counts with positive control mean, a positive fold threshold and viability fractions in [0,1]. The tool returns both means, their ratio, an inclusive viability flag and an inclusive fold screen gated by viability. Replicate lists need not be the same length.

foldIncrease=meanTreated/meanControl; flag=viabilityAdequate AND foldIncrease≥minimumFold

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
meanTreatedRevertants	Mean treated revertants	number
meanControlRevertants	Mean control revertants	number
backgroundFoldIncrease	Background fold increase	number
assayViabilityAdequate	Assay viability adequate	boolean
screenFlag	Screen flag	boolean

json

{
  "input": {
    "treatedRevertantCounts": [
      30,
      40
    ],
    "controlRevertantCounts": [
      10,
      10
    ],
    "minimumFoldIncrease": 2,
    "treatedViabilityFraction": 0.9,
    "minimumValidViability": 0.8
  },
  "output": {
    "meanTreatedRevertants": 35,
    "meanControlRevertants": 10,
    "backgroundFoldIncrease": 3.5,
    "assayViabilityAdequate": true,
    "screenFlag": true
  }
}

Limitations and assumptions

This does not establish definitive mutagenicity, statistical significance or a dose-response pattern. Strain, controls, metabolic activation and assay design are not assessed by the count ratio.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Lists are limited to 100,000 entries; the rules above may require smaller limits. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.

Alternative or Complementary methods

Use Fluctuation Culture Zero Class: Summarize fluctuation-test culture dispersion and the p0 mutation-event estimate from independent culture counts; not mutation frequency per cell. For a complementary task, use Viable Nonculturable Discordance: Screen discordance between viability assay and matched culturability; this pattern alone does not prove a VBNC state.

References

Ames Revertant Background Screen — tool.io

Similar or alternative tools

Fluctuation Culture Zero Class
Summarize fluctuation-test culture dispersion and the p0 mutation-event estimate from independent culture counts; not mutation frequency per cell.
Viable Nonculturable Discordance
Screen discordance between viability assay and matched culturability; this pattern alone does not prove a VBNC state.