Global Mean Delta CT

Normalize target Ct values to a reference-gene global mean.

Description

A global reference Ct mean supplies one baseline for all target values.

A global reference Ct mean supplies one baseline for all target values. Subtracting it is a Ct normalization step, not an efficiency-corrected fold-change calculation.^[1]

Normalize target Ct values to a reference-gene global mean.

When to use Global Mean Delta CT

Use this tool to normalize target Ct values to a reference-gene global mean.

Prepare the upstream counts, expression values, sequences or record lists requested by this tool. Keep corresponding features in the same order and confirm count units, transformations and caller-selected criteria.

How to use Global Mean Delta CT and understand its results

Prepare the upstream counts, expression values, sequences or record lists requested by this tool. Keep corresponding features in the same order and confirm count units, transformations and caller-selected criteria.
Enter targetCts, referenceCts using the field table and calculation rules, then run the tool.
Read referenceMeanCt, normalizedDeltaCts, meanDeltaCt. 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
targetCts	Target cts	list of number	Required
referenceCts	Reference cts	list of number	Required

Enter nonempty finite target and reference Ct lists; their lengths need not match. Average reference values, subtract that mean from each target and return the baseline, deltas and average delta Ct.

referenceMean=mean(referenceCts); deltaCt_i=targetCt_i−referenceMean

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

Output field	Meaning	Value type
referenceMeanCt	Reference mean ct	number
normalizedDeltaCts	Normalized delta cts	list of number
meanDeltaCt	Mean delta ct	number

json

{
  "input": {
    "targetCts": [
      25,
      27
    ],
    "referenceCts": [
      20,
      22
    ]
  },
  "output": {
    "referenceMeanCt": 21,
    "normalizedDeltaCts": [
      4,
      6
    ],
    "meanDeltaCt": 5
  }
}

Limitations and assumptions

No sample-pair matching, assay efficiency correction, control-condition comparison or undetected-Ct rule is used. The suitability of the reference pool is a caller assumption.

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.

Alternative or Complementary methods

Use Pfaffl Expression Ratio: Calculate Pfaffl expression ratio with independent primer efficiencies. For a complementary task, use Genorm M Value: Rate candidate reference genes by mean pairwise log-expression variation.

References

Global Mean Delta CT — tool.io

Similar or alternative tools

Pfaffl Expression Ratio
Calculate Pfaffl expression ratio with independent primer efficiencies.
Genorm M Value
Rate candidate reference genes by mean pairwise log-expression variation.